Simply Piano - Fast and fun way to learn piano
HapticKey - Trigger haptic feedback when tapping Touch Bar
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
TouchBar for your old MacBook - Use Touch Bar on an iPad through USB connection
Yousician - Learn to play music at home, at your own pace
Touch Bar Simulator - The macOS Touch Bar Simulator as a standalone app