Press B, A, or G to make the instrument play and show the fingerings as well as the notation for those notes. They will also play staccato so a student can play a song in a faster tempo. Attach a Makey Makey and use the space bar for B, the up arrow for A, and the down arrow for G (or use without a Makey Makey). These notes will play at a longer length for when you need to play songs with longer notes.
I thank Makey Makey and others who have used Scratch to code instruments.