One block, one note. Finish the tune.
Tap to drop a sliding slab onto the tower. Every block you place sounds the next note of the song, so the tune is built by the tower itself. Finish the tune to clear it and open the next one. Every song is out of copyright, and more are added over time.
Coins are picked up off the tower as you climb. They buy block colours, backdrops and instrument sounds, and nothing else. Nothing they unlock makes the game easier or changes your score. There is nothing to buy with real money.