GMMidi

GMMidi is a native GML script that lets you read and write MIDI files from your game. It is more or less a rewrite of this library, with some tweaks for GameMaker compatibility. Note that this extension is not for playing back MIDI files as audio, it's only for parsing and encoding.

• midi_parse(buffer) - Takes in a buffer that a MIDI file has been loaded into, and returns a struct containing parsed data
• midi_write(data, [options]) - Takes a struct that is the same format as returned by midi_parse() and converts it back into a buffer that can be saved as a MIDI file

The format of the struct returned by midi_parse() includes an array of MIDI events as they appear in the file. To make sense of the data, you may want to have the MIDI file spec handy.