TouchDAW - Full-featured DAW control and general purpose MIDI control app.
Helio Workstation - Cross-platform lightweight speed-painting tool for creating music.
XotoPad - MIDI instrument controller with chords, scales, faders, and more for multi-touch Windows devices.
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
Midi Studio - Full-featured, modular MIDI control surface for iOS
Guitar Pro 7 - Create, play and share your tabs