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General MIDI was first standardised in 1991, by the MIDI Manufacturers Association (MMA) and the Japan MIDI Standards Committee (JMSC), and has since been adopted as an addendum to the main MIDI standard. It has largely become a synonym for the acclaimed Roland Sound Canvas module. Other companies have created their own extensions to the original General MIDI standard, notably Roland GS Extensions and Yamaha's XG . GM itself was later revised to become '' GM Level 2 '' in 1999 and included some features common to GS and XG. MINIMAL FEATURE REQUIREMENTS General MIDI Level 1 compatible instruments are required to be able to:
PARAMETER INTERPRETATIONS GM Instruments must also obey the following conventions for program and controller events: Program change events This table shows which instrument sound corresponds to each program change number: Melodic sounds
Percussion notes Channel 10 is reserved for Percussion under General MIDI; this channel always sounds as percussion regardless of whatever program change numbers it may be sent, and different note numbers are interpreted as different instruments:
Controller events GM also specifies which operations should be performed by several controllers: 1 Modulation 6 Data Entry MSB 7 Volume 10 Pan 11 Expression 38 Data Entry LSB 64 Sustain 100 RPN LSB 101 RPN MSB 121 Reset all controllers 123 All notes off RPN The following global Registered Parameter Numbers (RPNs) are also standardised (the parameter is specified by RPN LSB/MSB pair and the value is set by Data Entry LSB/MSB pair): 0,0 Pitch bend range 1,0 Master Fine tuning 2,0 Master Coarse tuning 127,127 RPN Null System Exclusive messages Two GM System Exclusive ("SysEx") messages are defined: one to enable and disable General MIDI compatibility, on devices which also allow modes which are not GM-compatible; and the other to modify an instrument's master volume. GS EXTENSIONS The first GM synthesizer in Roland Sound Canvas line featured a set of extensions to General MIDI standard. The most apparent addition was the ability to address multiple banks of sounds by using additional pair of controllers, cc#0 (Bank Select MSB ) and cc#32 (Bank Select LSB ), to specify up to 65536 'variation' sounds. Other most notable features were 9 Drum kits with 14 additional drum sounds each, Control Change messages for controlling the send level of sound effect blocks (cc#91-94), entering additional parameters (cc#98-101), portamento, sostenuto, soft pedal (cc#65-67), and model-specific SysEx messages for setting various parameters of the synth engine. GENERAL MIDI LEVEL 2 In 1999, the standard was once again updated to include more controllers, patches, RPNs and SysEx messages. Here's a quick overview of the changes in comparison to GM/GS:
Additional melodic instruments can be accessed by setting CC#32 to 121 and then using CC#0 to select the bank before a Program Change. The most expanded group is Acoustic Pianos. SEE ALSO EXTERNAL LINKS
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