10a GM Instruments

Description

This patcher demonstrates how to choose a General MIDI (GM) instrument in Max. The General MIDI specification allows a maximum of 16 different instruments to be played at the same time. Each instrument has its own channel 1-16, inclusive. As we will explore in the next patcher, GM Channel 10 is reserved for percussion. The patcher is explained in bullet-point fashion below:

• This program generates random pitches within specified ranges (see Offsets).
• A random number (0-35) is chosen.
  
• The pitch offset is 48, producing the range of pitches 48-83 inclusive.
  
• The velocity offest is 64, producing the range of velocities 64-99 inclusive.
• The makenote object's default velocity is 64, and its default duration is 500 ms.
  
• Click on the noteout object and connect it to a GM-compatible synth; e.g., Max's default synth.
  
• General MIDI has 16 channels. In this patcher above, the noteout object is current configured to send messages to MIDI channel 1.
  
• The pgmout object, which is also configured to send messages to MIDI channel 1, is a MIDI object that sends a program change command to the selected device.
• Click on the pgmout object and connect it to the same GM-compatible synth. An instrument in the GM 1 sound bank is selected by supplying pgmout's left inlet with a number 1-128, inclusive.
• We created a umenu object that contains all of the program numbers and instruments names side-by-side so it's easy to choose an instrument. The instrument may be set to any one of the 128 instruments in the GM 1 sound bank via the umenu object. (Notice that the menu adds an offset of 1 to each instrument number).

New Objects

• pgmout – Send a MIDI program change command to a synthesizer
  
• umenu – A user-interface object that allows you to create a menu within the patcher
  

Object Reference

• +
• makenote & noteout
• random
• tempo
  

Reference

Hass, Jeffrey. 2025. "Chapter 3 MIDI, Section 3.9 Non-code MIDI Extensions (SMF & GM)." In Introduction to Computer Music: An Electronic Textbook. Bloomington, IN: Indiana University. Available online at: <https://cmtext.com/MIDI/chapter3_non-code_MIDI_extensions.php>.

MIDI Links

• The MIDI Association (TMA) – MIDI.org
  
  • General MIDI (GM) Specification
  • General MIDI 1 {MIDI.org}
  • General MIDI 2 {MIDI.org}
    
• The GM 1 Sound Set 
  • Square Space, GM Instrument Map {SquareSpace.com}
  • Carnegie Mellon, GM Percussion Key Map {cmu.edu}
• Max’s Built-in General MIDI Synthesizers {Cycling ’74}
  • Mac OS: Apple Audio Unit DLS (Down-Loadable-Sounds) synthesizer
  • Windows: Microsoft GS Wavetable synthesizer

Updated: 9/24/25