I'm pretty sure that I didn't know about Helio Workstation before this. It looks very interesting, and it's free too! Here's the app store description:
Helio is the cross-platform lightweight music creation playground.
Developed by musician with the dream of a perfect speed-painting toolbox, it features linear-based sequencer with clean UI, integrated version control to sync the projects between devices, export to midi and more.
Available for tablets and desktops.
Freeware, no ads, no in-app purchases.
- added MIDI files export (accessed via iTunes file sharing),
- added settings page with UI themes selection,
- implemented interactive dragging of the chord menu,
- various minor fixes.