We created this robotic glockenspiel from parts that we already had and made.
It is still experimental and is in version one.
The Spielatron is controlled by an Arduino which plays Midi commands sent to it from a PC.
Present limitations are
It is monophonic ie can only play one hammer at a time.The servo speed limits either the beats per minute or the note length of the music eg you cannot play a semi quaver at 120 BPM.”

Link