The Yamaha SY77 is Yamaha's most fully featured FM synth of it's era. As well as having a PCM engine similar to the ubiquitous M1, it has a 6 Operator structure with up to 4 layers per patch! The Operators include all the waveforms from the TX81Z but with a full 6 operators. Unique features to this synth include: user uploadable PCM samples that can be used as modulators in the FM engine, 4 stage looping envelopes and multimode filter and effects sections. Full Polyphonic sequencer is also included.
If you are looking for the ultimate FM synthesizer, look no further!