While I rarely post macOS only things, and never macOS only things based on a fucking gimmick, this official Samplr for Touchbar from Marcos Alonso looks pretty amazing. If you have a MacBook Touch Bar this is definitely worth checking out and it is totally fee. Unfortunately it requires Catalina.
Free download: http://samplr.net/touchbar/
Samplr for Touchbar is a demo of Samplr for the MacBook Touch Bar. The app uses the multitouch display of the Touch Bar to play samples in four different ways with multiple controls and effects.
If you want to experience the full Samplr app please check out the iPad version: http://samplr.net/