M-Audio 49i manual Channels, General Midi, Patches and the GM drum kit, Multi-Timbral, Polyphony

KeyStudio 49i User Guide 13

16 Channels

It is no coincidence that M-Audio GM Module has 16 channels. The definition of the MIDI standard specifies 16 MIDI channels for every MIDI connection. This means that up to 16 independent data streams (carrying Note On/Off messages etc.) can be transmitted at the same time. M-Audio GM Module makes use of all of them and can simultaneously play a different instrument on each of its 16 synthesizer channels. Always match the MIDI channel(s) you transmit on to the desired channel(s) of M-Audio GM Module. Channel 10 plays a special role in General MIDI compatible synthesizers. You will always find the GM Drum Kit on this channel.

General MIDI

General MIDI is where M-Audio GM Module got its name. GM stands for General MIDI. While MIDI defines the principle used for communication between musical instruments, the General MIDI standard defines what kind of sounds and features a GM-compliant synthesizer has to offer. This was necessary for compatibility between musicians and songwriters. Imagine the following situation: Musician A creates a MIDI song and sends it to Musician B for further refinement. They are both using different synthesizer models and when musician B plays the song back, it sounds completely different from what musician A had intended. The GM standard dictates that a compliant synthesizer has to have 128 standardized instruments (also called Patches) that are sorted and numbered a certain way. As an example, the first instrument in a GM compliant synthesizer is always the Acoustic Grand Piano. If musicians A and B are both using synthesizers that are GM compliant (regardless of the make and model of the synthesizer), then the song will sound very similar when played back on either one of them. Many of today’s synthesizers are General MIDI compliant or can operate in a mode that allows for this. M-Audio GM Module is based on the General MIDI standard. Its instrument categories, instruments, effects and settings are according to GM standard for maximum compatibility.

128 Patches and the GM drum kit

As explained in the previous paragraph, General MIDI defines the 128 instruments (also called patches) a synthesizer has to offer to be GM compliant. A complete list of GM patches can be found in Appendix A. Additionally, and also according to General MIDI standard, M-Audio GM Module provides a Drum Kit on channel 10. All the used drum- and percussion sounds are mapped to the keys as defined by the GM standard. A GM drum mapping chart can be found in Appendix B.

Multi-Timbral

Multi-Timbral means, that a synthesizer can produce multiple instrument sounds at the same time. For example, play Piano on channel 1, Bass on channel 2 and Drum sounds on channel 10 – all at the same time. M-Audio GM Module can play different instruments on all of its channels simultaneously and is therefore 16x multi-timbral.

Polyphony

The polyphony of a synthesizer stands for the number of notes it can play simultaneously. Some older synthesizers have very limited polyphony. For example, if a synthesizer has a polyphony of only 3 notes, you can play a 3-note chord with your left hand without problems. However, once you attempt to play an additional note with your right hand, you exceed the maxium polyphony by attempting to play 4 notes at a time. As a result, one of the notes played with your left hand will stop playing in favor of the new note triggered with your right hand. M-Audio GM Module has no such limitation and allows you to play as many notes at the same time as your computer’s CPU can handle.