The Geo Composer app is a free Android app for making music. You have two main instruments: a synth with a single sound and the piano. Then there is a percussion generator and everything looks like a piano chart/drum sequencer. There are many subdivisions to the timeline and they would only fit on a 10" tablet. The app does not play in background, but it can play over other songs. The 16x16 timeline can be set to play in most key: A, A#, B, B#, C, C#, D, D#, E, E#, F, F#, G, G# and in most scales: major, minor, pure minor, dorian, flamenco, mixolydian, lydian and harmonic minor. You can have four tones for each instrument, a volume slider, reverb level and decay, delay level and decay and you can set the time signature: 1/4, 1/4., 1/8, 1/8., 1/8T, 1/16 and 1/16. . You can pause or play the sequence, and you can have 8 sequences per each instrument. You can save as much 18 compositions, and load them as well as make a new start-up file. This app is any goon only on a large screen tablet.