Clapping Music, from the British app shop Touchpress, is a gamified lesson in tempo. It plays 13 different drum-like audio patterns, then asks players to replicate them by tapping on the screen. When you perform the first sequence correctly, you're automatically promoted a rung. If you can succeed at every level—and that's a big if, because this game is hard—you win.

Before it was an iOS game, Clapping Music was a piece of music Steve Reich composed in 1972 without instruments. To play it, one person claps out a basic rhythm. A second player joins in but shifts the rhythm slightly and eventually rejoins the first player's beat. It's incredibly difficult to do without getting thrown off, but when performed the way it was intended, the clapping creates an ecstatic symphony.

Touchpress created its mobile tutorial after the London Sinfonietta approached the studio with the mission of engaging a new audience with Reich's material. Alan Martyn, a producer at Touchpress, says the design team quickly realized that a game was the right approach, but that in order to work, it needed to be genuinely fun and not bang-your-head-against-the-wall frustrating—a big risk for a game involving ceaseless tapping.