General MIDI

General MIDI (GM) is a series of standards defining a minimum set of features for MIDI-controlled synthesizers.

The original and most widely-used version is General MIDI System Level 1 (GM 1), first published in 1991. Most references to "General MIDI" or "GM" without further explanation refer to this version.

There are several standards extending GM 1:

• Roland GS (first released 1991), Roland's proprietary extension
• Yamaha XG (first released 1994), Yamaha's proprietary extension
• General MIDI System Level 2 (first released 1999), the official successor incorporating some features of GS and XG

There is also General MIDI Lite, first published in 2004. This is a subset of the original standard intended for cellphone ringtones and similar applications.

The remainder of this page is only concerned with GM 1.

General requirements

A General MIDI-compliant sound generator must meet the following requirements:

Synthesis technology	No requirement (up to the manufacturer)
Available polyphony	24 voices (melody and percussion) or 16 voices (melody) + 8 voices (percussion)
Polyphony allocation	Dynamic
Channels	All 16
Channels are polyphonic	Yes
Key-based percussion	Always on channel 10
Minimum instrument presets	128 (GM Sound Set)
Minimum percussion presets	47 (GM Percussion Map)

Additionally, a General MIDI-compliant sound generator is recommended to have:

• A master volume control
• A MIDI input
• Left and right audio outputs for stereo
• Headphones connectors

General MIDI does not require a specific type of synthesis and leaves the specifics of how things sound up to the manufacturer. The names of instruments in the Sound Set and Percussion Map are guidelines.

The requirements of the General MIDI specification only apply when the sound generator is in General MIDI mode.

MIDI implementation

General MIDI requires that:

• MIDI note/key number 60 is Middle C
• Velocity is supported for all voices, including for percussion
• Voices are dynamically allocated
  • Notes can re-attack, including for percussion
• Channel Pressure (Channel Aftertouch) is supported
• Pitch Bend is supported

The default settings on each channel must be:

Pitch bend	0
Volume	100 (127 is the max volume)
Controllers	"normal"
Pitch bend sensitivity	±2 semitones

The following Control Change messages must be supported:

Ctrl #	Controller name
1	Modulation
7	Volume
10	Pan
11	Expression
64	Sustain
121	Reset All Controllers
123	All Notes Off

The following Registered Parameters must be supported:

RPN	Description
0	Pitch Bend Sensitivity
1	Fine Tuning
2	Coarse Tuning

SysEx messages

General MIDI defines two System Exclusive messages:

Message	Name
F0 7E 7F 09 01 F7	Turn General MIDI System On
F0 7E 7F 09 02 F7	Turn General MIDI System Off

The third byte (underlined) in both messages is a device ID. It is usually 7F for "broadcast". The "System Off" message is only meaningful for devices that also have a non-General MIDI Mode.

The "General MIDI System On" message is often called a "General MIDI Reset".

Sound Set

For channels other than channel 10, General MIDI defines a set of 128 sounds that can be selected with Program Change messages. The sounds are divided into 16 groups, as follows:

Piano

Prog #	Instrument
1	Acoustic Grand Piano
2	Bright Acoustic Piano
3	Electric Grand Piano
4	Honky-tonk Piano
5	Electric Piano 1
6	Electric Piano 2
7	Harpsichord
8	Clavi

Chromatic Percussion

Prog #	Instrument
9	Celesta
10	Glockenspiel
11	Music Box
12	Vibraphone
13	Marimba
14	Xylophone
15	Tubular Bells
16	Dulcimer

Organ

Prog #	Instrument
17	Drawbar Organ
18	Percussive Organ
19	Rock Organ
20	Church Organ
21	Reed Organ
22	Accordion
23	Harmonica
24	Tango Accordion

Guitar

Prog #	Instrument
25	Acoustic Guitar (nylon)
26	Acoustic Guitar (steel)
27	Electric Guitar (jazz)
28	Electric Guitar (clean)
29	Electric Guitar (muted)
30	Overdriven Guitar
31	Distortion Guitar
32	Guitar harmonics

Bass

Prog #	Instrument
33	Acoustic Bass
34	Electric Bass (finger)
35	Electric Bass (pick)
36	Fretless Bass
37	Slap Bass 1
38	Slap Bass 2
39	Synth Bass 1
40	Synth Bass 2

Strings

Prog #	Instrument
41	Violin
42	Viola
43	Cello
44	Contrabass
45	Tremolo Strings
46	Pizzicato Strings
47	Orchestral Harp
48	Timpani

Ensemble

Prog #	Instrument
49	String Ensemble 1
50	String Ensemble 2
51	SynthStrings 1
52	SynthStrings 2
53	Choir Aahs
54	Voice Oohs
55	Synth Voice
56	Orchestra Hit

Brass

Prog #	Instrument
57	Trumpet
58	Trombone
59	Tuba
60	Muted Trumpet
61	French Horn
62	Brass Section
63	SynthBrass 1
64	SynthBrass 2

Reed

Prog #	Instrument
65	Soprano Sax
66	Alto Sax
67	Tenor Sax
68	Baritone Sax
69	Oboe
70	English Horn
71	Bassoon
72	Clarinet

Pipe

Prog #	Instrument
73	Piccolo
74	Flute
75	Recorder
76	Pan Flute
77	Blown Bottle
78	Shakuhachi
79	Whistle
80	Ocarina

Synth Lead

Prog #	Instrument
81	Lead 1 (square)
82	Lead 2 (sawtooth)
83	Lead 3 (calliope)
84	Lead 4 (chiff)
85	Lead 5 (charang)
86	Lead 6 (voice)
87	Lead 7 (fifths)
88	Lead 8 (bass + lead)

Synth Pad

Prog #	Instrument
89	Pad 1 (new age)
90	Pad 2 (warm)
91	Pad 3 (polysynth)
92	Pad 4 (choir)
93	Pad 5 (bowed)
94	Pad 6 (metallic)
95	Pad 7 (halo)
96	Pad 8 (sweep)

Synth Effects

Prog #	Instrument
97	FX 1 (rain)
98	FX 2 (soundtrack)
99	FX 3 (crystal)
100	FX 4 (atmosphere)
101	FX 5 (brightness)
102	FX 6 (goblins)
103	FX 7 (echoes)
104	FX 8 (sci-fi)

Ethnic

Prog #	Instrument
105	Sitar
106	Banjo
107	Shamisen
108	Koto
109	Kalimba
110	Bag pipe
111	Fiddle
112	Shanai

Percussive

Prog #	Instrument
113	Tinkle Bell
114	Agogo
115	Steel Drums
116	Woodblock
117	Taiko Drum
118	Melodic Tom
119	Synth Drum
120	Reverse Cymbal

Sound Effects

Prog #	Instrument
121	Guitar Fret Noise
122	Breath Noise
123	Seashore
124	Bird Tweet
125	Telephone Ring
126	Helicopter
127	Applause
128	Gunshot

Percussion Map

General MIDI reserves channel 10 for key-based percussion and defines a set of 47 percussion sounds that can be played with Note On/Note Off messages. The sounds are as follows:

Note	Note #	Drum sound
B1	35	Acoustic Bass Drum
C2	36	Bass Drum 1
C♯2	37	Side Stick
D2	38	Acoustic Snare
D♯2	39	Hand Clap
E2	40	Electric Snare
F2	41	Low Floor Tom
F♯2	42	Closed Hi Hat
G2	43	High Floor Tom
G♯2	44	Pedal Hi-Hat
A2	45	Low Tom
A♯2	46	Open Hi-Hat
B2	47	Low-Mid Tom
C3	48	Hi Mid Tom
C♯3	49	Crash Cymbal 1
D3	50	High Tom
D♯3	51	Ride Cymbal 1
E3	52	Chinese Cymbal
F3	53	Ride Bell
F♯3	54	Tambourine
G3	55	Splash Cymbal
G♯3	56	Cowbell
A3	57	Crash Cymbal 2
A♯3	58	Vibraslap
B3	59	Ride Cymbal 2
C4	60	Hi Bongo
C♯4	61	Low Bongo
D4	62	Mute Hi Conga
D♯4	63	Open Hi Conga
E4	64	Low Conga
F4	65	High Timbale
F♯4	66	Low Timbale
G4	67	High Agogo
G♯4	68	Low Agogo
A4	69	Cabasa
A♯4	70	Maracas
B4	71	Short Whistle
C5	72	Long Whistle
C♯5	73	Short Guiro
D5	74	Long Guiro
D♯5	75	Claves
E5	76	Hi Wood Block
F5	77	Low Wood Block
F♯5	78	Mute Cuica
G5	79	Open Cuica
G♯5	80	Mute Triangle
A5	81	Open Triangle

Resources

• The MIDI Association's page on General MIDI
• General MIDI System Level 1 Specification (free download, login required)
• General MIDI System Level 1 Developer Guidelines (free download, login required)