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  1. Max Dobroselsky
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  4. Saturday, 01 February 2020
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I have several questions regarding percussion in GM 2 specification.

  1. In GM 2 we should select percussion set first and then select instrument. In ORCHESTRA set there are duplicated instruments. For example, Concert SD stands for both 38 (D) and 40 (E) notes. How should we deal with this cases? When I want to send Concert Snare Drum, what note should I use? Any? And when I receive either 38 or 40 note, should I treat both ones as Concert Snare Drum? Why GM 2 percussion spec contains ambiguity?
  2. To send percussion notes we should send Note On/Note Off events pairs always prepended with bank select events, am I right?
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  1. You first send the bank select MSB/LSB to make the channel a rhythm channel. Currently the GM2 spec only specifies 78H/00H. See section 3.3.1. Then you use a Program Change message to choose the percussion sound set.
  2. No, the 78H/xxH specifies your intention to use the channel as a rhythm channel. You use the Program Change message to choose a percussion sound set. A Program Change message is what you normally use to choose an instrument in a melody channel. See page 18 of the MIDI 1.0 spec. The xx can only be 0 (for a rhythm channel) in the current GM2 spec.
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  1. more than a month ago
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1. Both notes are the same instrument. They are useful if you want to do a snare roll where the notes happen very quickly. By alternating between the two notes you can get a better sound because you hear more of the waveform for each note.
2. No. You only send a bank change to specifically select a channel as a rhythm channel. After that you can send note on/off messages for the rest of the sequence.

See section 2.4 of the GM2 specification.
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  1. more than a month ago
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Thanks for the answer!

Yes, I read section 2.4, but still have questions:

  1. So I send percussion set change events (bank lsb/msb) and then send only notes and those notes will be treated as percussion within specified percussion set?
  2. In section 2.4 written: Any Channel can be used as a Rhythm Channel by sending the Bank Select message 78H/xxH followed by a Program Change message. What this Program Change message? I understand this text as: send 78H/xxH where xx is the number of percussion set, 48 for ORCHESTRA for example. Or 48 stands for program change? so what is the xx?
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  1. more than a month ago
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Thank you a lot!
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You're welcome.
Let us know if you have any other questions. There are many knowledgable folks here. :)
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  1. more than a month ago
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