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unmo3 (opensource)

3 Jan 2015, v0.61

Copyright Laurent Clévy (

This code is under GPLv2 license, with exception to mo3_unpack.c/.h under BSD now.



The piece of code has been written as a compagnion (validation code) of the document "the unofficial MO3 specification".


It is targeted to developpers or technical people, not for end users. It can be used by IT/XM/S3M modules specialists (tracker editor developper or modules players) to write a MO3 import loader, or more generally to handle MO3 modules in any way.

The MO3 format has been created by Ian Luck ( If you are looking for a good encoder and decoder (but without the source code) and a good module player, Ian's web site is the right place to go.

Features of unmo3 (opensource version)

Here they are:

  • uncompress the MO3 header and samples with lossless compression
  • able to save uncompressed header and samples
  • able to extract mp3 and ogg compressed samples
  • can display a channel of a given pattern into 2 forms
    • as encoded inside MO3 file
    • as it is usually appears in a tracker editor

This code has been written under Cygwin/IA32, should work under Linux/IA32, and is supposed portable under other architectures.

If you want to run the auto tests, you have to download "".


unmo3 [options] filename.mo3

available options are:

-a parselevel (from 1-4)
Display content of the MO3 file with more (-a 4) or less (-a 1) details

-d debuglevel (2)
Display some inner-working information

-v pattern_number voice_number
Display a channel of a given pattern as encoded inside MO3 module (technical output)

Must be combined with -v. Display a given channel, but as seen in any tracker editor (user friendly output).

-h header_output_filename
Write the uncompressed MO3 header into a file, for further study for example.

-s sample_number | all
Save one sample, or all samples of the MO3 module.


To build the executable

$ make dep
$ make

Demo: you can try

$ make demo

to see a 'demo'


$ make test

for the auto tests : mainly to check the decompression routines ("" archive is required).

Not provided with this code

There is remaining work to do to interpret how all IT/XM and S3M effects and samples/instruments parameters are stored AND interpreted by a player.

This work has been done by Johannes Schultz (sagamusix) from openMPT, thanks to him !

Have fun.



open source MO3 decompression and decoding support (but not playback)



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