Solution: piano brick with events that when the person playing it types "A", it plays an A. Seems easy.
Wow. That just got me thinking of a new addon.
It would be limited but could work.
In the text bar, type in /piano "2G 2F 4Eb 2G 2F 4Eb 1Eb 1Eb 1Eb 1Eb 1F 1F 1F 1F 2G 2F 4Eb"
The piano addon would then play the notes as described, I used 1s as eighth notes, 2s as quarter notes, and 4s as half notes. This could be a new way of making music on Blockland.
Other commands that could be used could be /piano *(90) #(4/4) "2G..." *for tempo and #for time signature. This could be an epic addon