Just click on one of the black or white blocks. It will play a song. If you want a specific song that isn't on the board, just say the name in the comments and I'll try to fit it on. GLITCH: you have to wait for the song you are listening to to finish before clicking a new one, or it will play two songs at once. You can also just click the green flag if you wish to pick a different song.
Credit to Jingyiw21_lms for the idea of songs.