Simply Piano - Fast and fun way to learn piano
keezy - A colorful soundboard. Play with music.
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
SoundGrail - SoundGrail Music App designed for pianists, guitarists, and DJs.
Yousician - Learn to play music at home, at your own pace
Aftertouch - Aftertouch – 3D MIDI Controller created and published by Kevin Nelson.