.XM File Format – Patterns

FastTracker 2 Extended Module

Each pattern has a header and then its packed notes, with no alignment between them. The number of patterns is in the file header. Numbers are little-endian.

Packing

An unpacked note is five bytes: note, instrument, volume column, effect type and effect parameter. Rows are stored channel by channel, one cell after another. Each cell starts with one byte:

  • If its top bit is clear, the byte is the note, and the other four fields follow.
  • If its top bit is set, the byte is a control byte, and only the fields it names follow.
BitValueMeaning when set
001A note byte follows.
102An instrument byte follows.
204A volume column byte follows.
308An effect type byte follows.
410An effect parameter byte follows.
5–6Unused.
780Set: this is a control byte.
 
83 31 01  80  3D 02 40 0A 05
Three constructed cells. 83 is note and instrument: note 31 (C-4), instrument 1. 80 is empty. 3D has its top bit clear, so it is the note (C-5), followed by instrument 2, volume 40, effect A and parameter 05.

Fields

FieldValues
Note1 to 96, C-0 to B-7; 97 is key off; 0 is no note.
Instrument1 to 128; 0 is no instrument.
Volume columnBelow.
Effect type0 to 35, for effects 0 to Z.
Effect parameterThe effect’s parameter.

Volume column

ValueShown asMeaning
00Do nothing.
10–50v00–v64Set volume: the value minus 10.
60–6FdVolume slide down.
70–7FcVolume slide up.
80–8FbFine volume slide down.
90–9FaFine volume slide up.
A0–AFuSet vibrato speed.
B0–BFhVibrato depth.
C0–CFpSet panning.
D0–DFlPanning slide left.
E0–EFrPanning slide right.
F0–FFgTone portamento.

The low four bits of each range hold its value. Volume slides here do not remember their parameter. The vibrato speed and depth share memory with effect 4xy; tone portamento shares memory with 3xx.