401 lines
17 KiB
Plaintext
401 lines
17 KiB
Plaintext
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-------------------------------------
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## Impulse Tracker MIDI Supplement ##
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-------------------------------------
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Introduction
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============
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The biggest new addition to Impulse Tracker 2.12 has been support for
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sending data out through the MIDI protocol. Earlier versions of Impulse
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Tracker (IT) have had support for incoming MIDI data, so it was possible to
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play on a 'MIDIfied' keyboard and have IT 'track' all the notes down in the
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pattern in realtime.
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MIDI out, however, is a completely different ballgame. You in fact don't
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have to read this supplement at all if you wish to get MIDI working, but in
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order to gain full usage of MIDI out, you will have to read this in order
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to understand how IT's MIDI support fully works
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MIDI Support & Soundcards (Modified by Pulse)
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=============================================
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At present, the only sound devices IT supports for MIDI output are the AMD
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InterWave and the Creative Labs Sound Blaster AWE32. Support for other
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soundcards is via the generic MPU401 driver. To use this driver, you must
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run "IT /S19 /A<address>" where <address> is the address of your MPU401
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compatible card (eg. "IT /S19 /A330"). Note that the generic MPU401 driver
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does *NOT* support sample playback at all.
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MIDI And AWE32 Soundcards (Pulse)
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---------------------------------
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I have found that the Windows '95 drivers for the AWE32 are somewhat buggy.
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On my computer, I can use MIDI In/Out in Impulse Tracker *IF* I disable the
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MIDI support within Windows '95. Otherwise, it is simply not recognised. To
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disable the MIDI support in Windows '95, right click on "My Computer",
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"Properties", "Device Configuration", "Sound, Video & Game Controllers".
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Double click on "Creative Labs SB16 or AWE32" and go to the resources.
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Uncheck the "Use Automatic Settings" box if it is set and change the basic
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configuration to one that does NOT include the MIDI Ports 300h or 330h.
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(For example, Basic Configuration 0 has only 220h, 5, 1, 5 on my computer
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and IT works fine in a DOS Box)
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Enabling MIDI
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=============
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To enable MIDI output, you must first have IT on Instrument control mode
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rather than Sample control mode. To do this, press F12 to go to the Song
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Variables screen and switch control to 'Instruments' if you haven't already
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done so.
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MIDI & Instruments
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==================
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MIDI Channel
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------------
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New to the Pitch section of the Instrument screen (press F4 and select the
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"Pitch" button) are the sliders "MIDI Channel", "MIDI Program" and "MIDI
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Bank". Once the MIDI Channel value for that instrument is set to a value
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other than zero, IT will send out MIDI data whenever that instrument is
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encountered in a pattern, on that particular MIDI Channel. What data IT
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actually sends through the MIDI port will be a note on command, although
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this will be discussed in more detail later.
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MIDI Program/MIDI Bank
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----------------------
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The MIDI Program and MIDI Bank sliders work in a similar manner to each
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other. If they have a value set to -1, IT will not transmit a program change
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message nor a bank change message for that instrument. If you specifically
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set a MIDI Program for that instrument, IT will send a 'program change'
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message along with the 'note on' message.
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The MIDI Bank instrument setting is also the same; IT will not send a bank
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change message if the MIDI Bank slider is set to Off (ie: has a value of
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-01). If the MIDI Bank setting is active for that instrument, IT will send
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it along with the note on message as well.
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Summary
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-------
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IT will always send a 'note on' command for a particular MIDI channel
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whenever a MIDI instrument is encountered in the pattern. (A MIDI instrument
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is simply an instrument where the MIDI Channel value has been set to
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something other than "Off"). IT will also send a program change command and/or
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a bank change command along with the note on command if they are set active.
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More Advanced MIDI
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==================
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How MIDI Works
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--------------
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MIDI is not a file format (like IT is a module format) nor is it even a file
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layout. MIDI is a computer protocol (or language) which is used to
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communicate between devices . You may like to think of it as a network,
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where the MIDI cables are the cables you lay between computers, and MIDI is
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the network protocol (such as Novell NetWare, Windows Networking or TCP/IP)
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used to communicate between the sound devices. When an instrument is said to
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be 'MIDI compliant', that means that it has support for the MIDI protocol
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and understands MIDI messages.
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The .MID file format is simply a way to store these messages. It is a
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collection of MIDI data, and when a .MID file is run through a MIDI player,
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all the MIDI player does is send the data in the .MID file out through the
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computer's MIDI port. In a network analogy, if you can imagine that every
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single transaction run through the network was being logged to a file on
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your hard disk; that every single byte was being recorded to a logfile, this
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is what a .MID file is.
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An example of MIDI Communication in IT
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--------------------------------------
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You've read above that when IT encounters a MIDI instrument in the
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patterndata, it sends a 'note on' command, which is defined in the MIDI
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protocol to be 'Play this note on this MIDI channel at this particular
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velocity'. (Velocity is similar to volume ). If you play a MIDI instrument
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which is mapped to MIDI channel 2 at C-5 with a velocity of 64, the actual
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data which IT sends out to the MIDI port resembles something like this (in
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hex):
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Note On with parameters;
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MIDI Channel: 2
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Note: C-5
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Velocity: 64
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Data that IT sends out (hex): 91 3C 40
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Data that IT sends out (decimal): 145 60 64
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We'll run through each of these three bytes step by step.
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The first byte (91 in hex, or 91h) is the actual 'Note on' command. It tells
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the receiving MIDI device that the data which follows is part of the 'note
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on' data. An analogy which trackers may find useful is the effect column.
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There, you have an effect command and effect data; for example, the effect
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'G20' can be split up into two parts--'G' and '20'. The 'G' part is the
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actual effect command which tells IT that you wish to perform a portamento,
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and the '20' part is the effect data, or in this case the spe ed at which
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the portamento should occur. In this MIDI example, the '9' is the MIDI
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command and the '1 3C 40' is the rest of the data for that command.
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Now, the second digit (1 in our example) specifies the MIDI channel. MIDI
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channels are 0-based; that is, if you want to send to MIDI channel 6, IT
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specifies 05 for the actual data. MIDI channel 10 is 09h, MIDI channel 14 is
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0Dh, etc. Here we're sending to MIDI channel 2, so the value sent out over
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MIDI is 01h.
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The second byte (3Ch) is actually the note to send (C-5 here). In MIDI, all
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command (parameter) data is between a scale of 00h-7Fh (or 0-127 in
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decimal). Notes are transmitted the same way - via numbers. If you imagine
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C-1 is sent with a value of 00h, C#1 i s 01h, D-2 is 02h, etc, then the note
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we want to play, C-5, has a value of 3Ch (60 decimal).
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Now the first and second bytes are done with, the third byte should be
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fairly easy to understand. This byte represents the velocity at which the
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note should be played. In our case, we want a velocity of 64, which
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translates to 40h, and so this is the value which is sent out.
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So to recap, we have three bytes for the note on command, "91 3C 40".
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Byte 1: 91 == Note on command (on MIDI channel #2)
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Byte 2: 3C == Note on data (Note to play, C-5)
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Byte 3: 40 == Note on data (Velocity of 64 decimal)
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Configuring IT's MIDI out data
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------------------------------
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Keeping the above example in mind, press Shift-F1 to get to IT's MIDI screen
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and press the 'MIDI Output Configuration' button. This will take you to IT's
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MIDI out engine. Now, if you examine the 'Note On' field, it reads:
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9c n v
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This can be correlated to our above example of '91 3C 40'. Now, the 'c n v'
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in the Note On field corresponds to 'channel', 'note' and 'velocity'. Think
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of them as variables; IT will substitute the appropriate channel, note and
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velocity values which it encounters in the MIDI instrument information
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and/or patterndata.
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If you now actually defined a MIDI instrument to play on MIDI channel 2, and
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you played it in a pattern at C-5 with velocity 64, all IT does is read the
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'Note On' field from the MIDI configuration screen and substitute '1' for
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'c', '3C' (C-5) for 'n' and '64' for 'v'. Therefore, IT will read '9c n v'
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and replace it with '91 3C 40'.
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In any of the MIDI output fields, lowercase letters represent variables (or
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subsitutions which IT should make) and uppercase letters or numbers are
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constants which IT writes to the MIDI port directly without any change.
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Therefore, these fields are case se nsitive--for the note on command, '9c n
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v' is blatantly different to '9C n v'. 9c represents 'send byte 09 followed
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by the MIDI channel byte', whereas 9C represents 'send the byte 9C'.
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In short, 0-9 and A-F are treated as hexadecimal constants and will be
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passed through directly. Lowercase letters will be treated as variables and
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substituted accordingly. Note that variables are regarded as 'full bytes' by
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themselves and are never part of an actual byte sequence except for the
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variable 'c', so '9n' is exactly the same as '09 n' or '9 n'; all of them
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will expand to the sequence '09 <MIDI note byte>'. 'c' is the only value
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that takes on a nibble (4-byte) value, due to the MIDI protocol definition.
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This means that 9c will actually become one byte when expanded, with the
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lower digit representing the channel.
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IT MIDI Variables
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-----------------
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c: MIDI channel
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This is simply the MIDI channel of which the instrument is set
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to, 0-based. Note that this is the only nibble sized variable.
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m: note value (instrument)
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A value from 00-7Fh representing the note to be played, where
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C-5 is 60h. This is the note entered in the pattern, not the
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translated value.
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n: note value (sample)
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A value from 00-7Fh representing the note to be played, where
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C-5 is 60h. This is the note after instrument translations have
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been applied.
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o: Offset value
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Extra parameter than can be sent via Oxx commands.
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v: velocity
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The MIDI velocity of the note.
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u: volume
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Volume is similar to velocity, except that velocity does not
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take the volume envelope and fadeout values into account, whereas the
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'u' volume variable does.
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x: pan set
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Sends a MIDI panning value. This does not take into account
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panning envelopes.
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y: calculated pan
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Sends a MIDI panning value which does take into account
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panning envelopes.
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a: high byte of bank select
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b: low byte of bank select
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These commands are only really useful in the bank change
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field.
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z: macro data
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(See section on macros for full explanation).
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Configuring MIDI Output for Your Keyboard
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-----------------------------------------
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In the basic IT distribution, the only fields which have any data are 'Note
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on', 'Note Off' and 'Program Change'. The reason for this is that these are
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the only commands which are set as standards by MIDI. MIDI commands such as
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Change Pan, Bank Select , e tc all differ from synth to synth. There's not
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much which can be done to solve this, you will have to look up your synth's
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manual to find out the exact MIDI commands it needs to issue a panning
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change, bank select, etc.
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Some values which you may wish to try, however, will be:
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Change pan: Bc 0A x
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Bank select: Bc 0 a 20 b
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These may or may not work. If they do, then great, but if they don't, you
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will have to actually RTFM *gasp* in order to get these other commands
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working.
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Effect Commands & Macros
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========================
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Now that IT's MIDI engine is understood and the basis of MIDI communication
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has been laid down, perhaps the most powerful function of IT's MIDI engine,
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macros, will be explained.
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Standard Effects
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----------------
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Firstly, at the moment there is NO support for standard IT effect commands
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(such as pitch slide, portamento, vibrato etc) to work via MIDI. This may or
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may not be implemented in future. Currently, however, if you perform an E01
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effect on a note, nothing w ill happen as far as the MIDI aspect of the
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instrument is concerned.
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Macro Effects - SFx
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-------------------
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The SFx command, previously used in the .MOD format as "FunkRepeat", has
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been changed in IT to allow for the functioning of MIDI macros. The unused
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Zxx command will also now play a part in MIDI functioning.
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To understand how this works, it's best to take an example into account. At
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the beginning of this supplement, the MIDI sequence '91 3C 40' was used
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which was a Note On, MIDI channel #2 played at C-5 with a velocity of 64.
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This was represented in IT's MIDI configuration as '9c n v', so it made the
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appropriate substitutions to '91 3C 40'.
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The Macro Setup section of IT's MIDI Output Configuration screen can be used
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to define your own custom MIDI command/data sequences. These can be
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absolutely anything you like, from a MIDI SysEx command to a Note On
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command. In fact, to start off, we'll tak e a Note On sequence as an example
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and we will attempt to emulate the same '91 3C 40' bytes, except that we'll
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make this sequence ourselves rather than letting IT do the work for us.
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How SFx and Zxx commands relate
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-------------------------------
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Firstly, remember that IT substitutes values when it encounters variables.
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If you glance at the above section on IT MIDI Variables, you'll notice that
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the 'z' variable represents macro data. Now that this '91 3C 40' sequence
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has been driven into our he ads, try setting the SF0 macro field on IT's
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MIDI Output Configuration screen to '91 3C z'.
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Remember that the third byte in the MIDI sequence (40 in our normal
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example) is the velocity to send with the Note On message. The SF0 macro
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field you've just defined means that IT will read any Zxx effects and
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replace the 'z' variable in the SF0 macro with the 'xx' value from the Zxx
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effect. To enable the macro, simply put in a SF0 along with a Note On in the
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pattern data. Now, all values from Z00 to Z7F will substitute for 'z'
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accordingly. So, to show that our SF0 sequence will reproduce the exact same
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thing as our Note On command:
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C-5 01 SF0 (this will play the note on command as usual, and
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specify that the SF0 macro sequence should be
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hooked to Zxx effects).
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... .. ...
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... .. ...
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... .. ...
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... .. Z40 (this will trigger our SF0 sequence with a 'z'
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value of 40h).
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The above patterndata should produce a note on event at row 0 in the
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pattern, and again at row 4. Now, try replacing the Z40 effect with Z7F and
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IT will substitute 'z' with '7F', or a velocity of 7Fh (127 decimal) in our
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SF0 sequence. The result should be that you'll hear a Note On with velocity
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64 on row 0, and a Note On with velocity 127 on row 4; ie: the second note
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triggered will be twice as loud. The The sequence that IT will send will be
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'91 3C 7F'.
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SFx commands summary
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--------------------
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Our example above of using a 'note on' command sequence for an SFx effect is
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rather pointless, since IT does this effect itself. However, it has
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hopefully served its purpose by demonstrating how effects work.
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The SFx commands, as you can see, can be redefined to absolutely any MIDI
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data at all. This can be something simple like a pitch slide, a complex
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SysEx 'set filter to aftertouch' command, or whatever you like. The
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possibilities are endless and are only li mited by what your synth can do;
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IT's SFx/Zxx combination is customisable enough to handle nearly any MIDI
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data you wish to output.
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If you wish to take advantage of these commands, you will have to look up
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the manual for your synth and get stuck into the MIDI/SysEx section. Please
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do not come to any IT support people asking for help on this subject because
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every synth is different.
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Z80 -> ZFF commands
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-------------------
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The Z80 to ZFF commands are also macro sequences, but they have no 'z'
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variable to substitute for. They are not 'hooked' to any SFx effects, they
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are straight, direct macro sequences. For example, if you have a MIDI
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controllable effects unit (such as an Alesis MidiVerb), you may wish to
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assign the Z80 command to set a up a certain value for the reverb delay
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length. Later in the song, you can issue a Z81 command to change the reverb
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delay or turn it off altogether.
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To summarise, the Z80 to ZFF commands are similar to SFx macro sequences,
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but they do not have any extra parameters (whereas the SFx macro's 'z'
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variables are controlled by Z00 to Z7F).
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Contact Information
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===================
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If there are any problems with this textfile, email ozone@post1.com or
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pulse@cyburbia.net.au
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__/\___/\_/\____/\____/\ .. . Andre Pang % vault ...:
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/ /__ / \_ \_ __) :.. mailto:ozone@post1.com . ....:
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( : / (__: ) | | _)_ : . http://www.mindflux.com.au/ .:
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\___( ______/|__;__|_____| :. irc: #trax (irc.neato.org) ..:
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\/ - #ozone
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