Editing works best on a computer. On a phone you can generate, listen and export.
Pick a mood to get a full arrangement you can edit, or start from an empty track.
SFX Brew Studio is a small music workstation that runs in your browser. Every song is made of tracks, every track of regions, every region of notes you can edit in the piano roll or drum grid. Nothing is uploaded: sound is synthesised on your computer.
Generate a piece from a mood (calm landscape, battle, mysterious cave, sorrow) and the composer writes a theme, harmony, sections, bass and percussion as separate tracks. Change the instruments, move regions, redraw the melody, mute and solo, set the cycle range and export a seamless loop or stems for your game engine.
Everything you make is free for commercial use, no attribution required. The few recordings used (drums, gong, erhu) are CC0.