Rock Hardbuns has released Piper 2, a free FM synthesizer instrument for Windows.
This is the second incarnation of my PM (a.k.a FM) synth.
Tighter, faster code. Wider range of sounds. Prettier GUI. Should still be pretty easy to program.
Featuring awesome anti-aliasing filter (derived from code by Dave from Muon. Cheers!). The button labeled AA turns it on.
Piper is available as a freeware VST instrument plug-in for Windows PC.