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The project file format

Fabian S. edited this page Jun 22, 2026 · 1 revision

In version v2.0 and onwards, .mdj files are JSON files with the following structure:

{
	"bpm": 80,
	"data": [
		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
	],
	"format": 1
}

format

The file format version. Current version is 1.

bpm

The tempo in beats per minute. Must be greater than 0.

data

Contains four arrays, each one representing a single instrument track. They are played simultaneously and must have the same size.

Every number represents a sample index:

Sample names and indices

Name Index
Empty tile 0
Introduction
Groove 1 1
Groove 2 2
Salsa 1 3
Salsa 2 4
Reggae 1 5
Reggae 2 6
Techno 1 7
Techno 2 8
Verse
Groove 1 9
Groove 2 10
Salsa 1 11
Salsa 2 12
Reggae 1 13
Reggae 2 14
Techno 1 15
Techno 2 16
Chorus
Groove 1 17
Groove 2 18
Salsa 1 19
Salsa 2 20
Reggae 1 21
Reggae 2 22
Techno 1 23
Techno 2 24
Solo
Groove 1 25
Groove 2 26
Salsa 1 27
Salsa 2 28
Reggae 1 29
Reggae 2 30
Techno 1 31
Techno 2 32

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