As a leaving gift for my music teacher, I built a stylaphone with an inbuilt puzzle.
If the correct sequence of notes is played, Morse code is buzzed. In the example below the note sequence is C, A#, E and the Morse code spells out “miles” (although the full message is longer).
The project is made from:
The board was a 5*7cm universal PCB which I added large squares of solder onto to act as the contacts for the stylus.