The Frozen Synapse Website now offers online sales of the full soundtrack for Frozen Synapse (thanks Morris). They provide a sample, and the following explanation of the implications of buying it from them rather than elsewhere:

(PLEASE NOTE - Other distributors (such as Valve) may choose to offer the soundtrack at a lower price if you have already purchased the full game outside of a Soundtrack Edition bundle. If you are in this position, but would like to support Mode 7 and nervous_testpilot further, you are welcome to choose to pay more and buy direct from us. This will encourage the creation of more music and other ambitious indie game soundtracks! However, please also feel free to shop around.)