Rock Hardbuns has released Piper 2, a free FM synthesizer instrument for Windows.
Rock writes:
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.