FM Ogre (FM Operator with GRatuitous Enhancements) - a dsPIC33FJ64GP802 running custom software, to do true FM synth work. The idea is to be able to generate those wonderful clangorous FM sounds that the DX7 of yore could do so well. It's an "operator", not an oscillator, hence it starts with sine waves and Bessel functions and does everything from that. There is no "saw / square / triangle" output (although you can approximate those waves, and many more, via the distortion / self feedback capability.)

Specs: input rate: 41 KHz@12 bits, output 83KHz@16 bits with 256x interpolation, V/octave control from ~1 Hz to 32 KHz. Linear frequency modulation authority: +/- 10KHz at maximum FM index (through-zero, FM index has a separate input channel on the ADC); linear phase control authority +/- 9*pi angle, wavelength matched (phase modulation index is also a separate input from phase mod input). Frequency stability of core: +/-40ppm (crystal controlled). Feedback operator authority:in excess of 8x Hz (through zero as well, of course). Also has hard sync in and out (TTL-level compatible)