I’m not sure how Graham Parks is doing it but it he seems to be using the GarageBand sound library to power the music generation. Touch Bar Piano is not on the official App Store but it is free to download from the utsire website. As such the app is unsigned so you’ll have to get ackledulge and dismiss all the security warnings that will pop up. It is goes without saying that you also need to have a MacBook Pro with Touch Bar to play around with it. If you don’t have the new mac the app is basically useless to you. To use it go into System Preferences -> Keyboard and pick ‘Touch Bar shows App Controls’. Check out the video below.