Create sequences and order them.
Fill your patterns with the included controlers.
Using soundfonts allow you to easily change the sound bank of a composition using General MIDI soundfonts.
Connect external MIDI inputs controllers and/or MIDI outputs sound modules.
WARNING: MIDI feature is not supported by every Android devices. Consult the specifications of your device to see if it supports MIDI connections.
User manual: http://www.volcanomobile.net/midi-sequencer/user-manual.html
This application uses a modified version of FluidSynth, you can find the source code here https://github.com/VolcanoMobile/fluidsynth-lite