Making Game Music the MIDI Way

As well as playing back digitised recordings of ‘real’ analogue music, many games make use of MIDI recorded soundtracks to “play” the music back in real time via a music synthesiser.

Originally design as a protocol for connecting physical keyboard based synthesisers to each other and to rack mounted, expander synthesiser boxes, MIDI – the Musical Instrument Digital Interface – soon became used more widely as a standard for recording musical sequences as a series of control signals that could be used to ‘play’ an computer musical instrument. Today, MIDI sequences can be used to control a wide variety of peripherals, including the onboard synthesiser on many computer sound cards, using a specification known as General MIDI (General MIDI 1 specification).

Following its introduction in 1991, General MIDI gained widespread support amongst manufacturers, enabling game publishers to make use of it to play ‘live’ their game soundtracks. (More recently, in 2007, GM1 was superceded by GM2. However, as GM1 continues to remain the de facto. standard, I shall not consider GM2 here.).

So what exactly is General MIDI?

General MIDI (GM)

The General MIDI specification describes a minimum specification synthesiser that can be guaranteed to play back a General MIDI sequence. GM synthesisers are supported by many sound cards, and by music players such as Quicktime and various Windows media players.

The General MIDI Level 1 specification required, among other things, “a minimum of either 24 fully dynamically allocated voices are available simultaneously for both melodic and percussive sounds, or 16 dynamically allocated voices are available for melody plus 8 for percussion. Support for all 16 MIDI channels, each capable of playing “a variable number of voices (polyphony). Each Channel can play a different instrument (sound/patch/timbre). A minimum of 16 simultaneous and different timbres playing various instruments. A minimum of 128 preset instruments (MIDI program numbers) conforming to the GM1 Instrument Patch Map and 47 percussion sounds which conform to the GM1 Percussion Key Map.”

To see what instruments and percussive sounds are supported by a GM1 synthesiser, see the General MIDI Level 1 Sound Set.

What GM1 MIDI instrument patch number corresponds to “Acoustic Guitar (steel)”? How many isntruments are in each GM1 instrument family? What instruments are available in the “Brass” instrument family? What GM1 percussion key number corresponds to a “Closed Hi Hat”?

If you would like to listen to any – or even all – of the sounds supported by GM1, why not try putting together your own GM1 composition, for example using the Online Midi Sequencer.

To create a MIDI track, select one or more instruments or percussion instruments, tick the left most checkbox to turn the instrument on, and click in the sequence checkboxes to select the beats on which each instrument will play. Click on create MIDI and the embedded player will play your sequence back to you.

Experiment with creating some simple sequences using the Online MIDI Sequencer. If you come up with a sequence you are particularly proud of, or think may go well with a particular game, why not take a screenshot of the settings, upload it to your blog (or maybe to an image sharing site such as flickr) and post a link to it back as a comment here, explaining how you think the sequence could be used ;-)

If you save your composition as a MIDI file, I think it should play in Game Maker…(?!)

Want to know more about MIDI?

To see how MIDI can be used in a digital music studio to interconnect a variety of computers and digital music synthesisers, read the Tutorial on MIDI and Music Synthesis on the MIDI Manufacturers’ Association website.

If you are interested in learning more about the actual format of MIDI sequences, this article on The MIDI File Format provides a good introduction.

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