TOPLAPapp is a sonic puzzle based around a virtual machine for sound synthesis. This machine accepts a few valid instructions represented by the letters T, O, P, L, A, and p, and you control it by placing each command letter within a grid, along with setting some associated parameter sliders. The machine rushes through the instruction set to create output sounds, which are usually of a somewhat noisy character, hopefully interestingly so. The historical antecedents include instruction synthesis as pioneered at the Institute of Sonology in the 1970s, and the live coding movement, of modifying a running program as it acts. This app is intended for those interested in more experimental sonic art: don't download unless you are open to stranger computer music sounds ((http://www.toplap.org).