Thiago Teixeira made this Coin Sequencer, which allows you to lay down tracks using spare change. It’s an older project (from before 2005?), but is new to me. As the turntable spins, the coins go under a row of infrared sensors, which send on/off signals to a computer to turn the music on and off. I like the simplicity of using a turntable and IR sensors- I recently made a project like this, but used a computer vision system and some custom hardware to achieve basically the same effect. Nice work! [Thanks, Stuart!]