Yamaha SY99chat_bubble_outlineFrom real comments

Owners consistently call the SY99 a legendary, deeply capable synth engine. Multiple long-term owners describe the SY99 as a monster synth with enormous complexity, combining AFM and AWM2 in ways later reused in the Montage decades later. Comments highlight custom algorithms, RCM synthesis, and feedback routing as features unmatched even by later Yamaha FM models, giving it lasting character and a devoted following among FM programmers.

The keybed and build quality draw near-universal praise. Several commenters single out the semi-weighted keybed with adjustable aftertouch as among the best ever fitted to a synth, and describe the chassis as built like a tank out of solid steel. This durability is credited with keeping decades-old units still fully functional today with only minor maintenance like battery or belt swaps.

Weight and interface complexity are the recurring frustrations. Multiple owners sold their SY99 specifically because it was too heavy to gig with, and others describe the AFM programming and menu-based UI as mind-bending or a full day's task to master. Acoustic samples like piano and sax are also noted as dated compared to modern standards, even though other synthesized and bell-like sounds are still praised as stunning.