Just been tipped off about this flying ball-bearing music machine (thanks Ben!). Would be great to combine this with the BeatBearing somehow, there’s a lot of possible design variations…

BEARINGS GLOCKEN is a musical instrument that automatically performs a glockenspiel using steel ball for bearings, said to be the world’s most perfect sphere on earth.
The steel ball is finished into a nearly perfect sphere, and has the property of uninformly bouncing back, over and over.
BEARINGS GLOCKEN uses this property in a musical instrument.

Project website: