Can you add such feature either by third-party extension or by part of sound extension? We can use libmodplug library for module playback.
The main advantage over mp3/ogg music files is that xm/it/mod files are usually smaller than mp3/ogg (though there are some exceptions when you’re using lots of samples) - it is basically like MIDI files, but with embedded sound table and only used sounds are embedded.
I second to this idea! 
Although I prefer the usage of the more modern libxmp instead of libmodplug. libxmp is currently well maintained and more stable.
I also want to propose a support for new module format, mo3 which is created by Ian Luck from Un4seen. It is basically a regular module format, but with one distinguish feature, OGG and MP3 as sample. Therefore it will greatly reduce the size of module format thus making it suitable for creating small and compact game.
Regards
Well, I think, whether we’d do it via libmodplug or libxmp, it’d be best to add support for all formats supported by the lib. XM/IT/S3M I gave only as examples since those are most well-known module formats.
And .mo3 seems like nice format. Do you know of any free trackers supporting it?
The best and most compatible free player is XMPlay which is made by the Mo3 creator itself. Playstation, SNES, SEGA Genesis, GBA, and many other video game music format can be played there as well and even you can convert them to streaming format, such as WAV and OGG Vorbis if you want.
No, I’m talking tracker, not player.
OpenMPT can edit Mo3 out of the box, but it cannot save the result to Mo3. You still need the official encoder to encoding the resulted Impulse Tracker to Mo3.