Timidity AE

Multimedia player focused on playing MIDI files. Instead of built-in Android
MIDI playing features, it uses Timidity++ engine and allows specifying
soundfonts and options. Included soundfont 8Rock11e seems to have non-free
license "Distribute freely. Don't disassemble."

Features include:

* High quality MIDI file playback far superior to Android's built in Synth
* Support for multiple user-set SoundFonts or patch sets
* Multi-track mixer with support for per-track instrument and volume adjustment (only available for MIDI and MOD files)
* Tempo, pitch, voice, and resampling controls
* Create, save, and load custom instrument and volume configurations
* Additional support for Amiga MOD files as well as the formats Android natively supports (mp3, ogg, flac, etc)
* Export MIDI or MOD files to wav
* Compressed .sfArk and .sfArk.exe SoundFont extraction
* Notification with playback buttons (Honeycomb or later)
* Folder and playlist based music organization
* Dark and light themes