The Yamaha SY99 is a synthesiser combining frequency modulation synthesis (branded as Advanced FM) and sample-based synthesis (branded as Advanced Wave Memory 2) and the direct successor to Yamaha's SY77/TG77. Compared to the SY77, it has a larger keyboard at 76 keys instead of 61, a larger ROM with more in-built AWM samples, the ability to load user-specified AWM samples into on-board RAM, an upgraded effects processor (based upon the Yamaha SPX900 rather than the SPX90), and several other enhanced features.
Polyphony: 16 notes of AFM + 16 notes of sample-playback (AWM2)
Oscillators: Each voice can have up to 2 AFM elements, each comprising up to 6 operators; plus up to 2 AWM elements
Filter: Multi-stage, time-variant, with resonance and self-oscillation
Sequencer: 16 tracks, ~27,000 note capacity, 99 patterns, up to 10 songs (cf. the SY77's single song only and ~16,000 notes)
Effects: 2 internal digital effects processors with 63 types of effects, derived from Yamaha's popular rack-mounted processor, SPX900
Keyboard: 76 notes with velocity and channel aftertouch, which can be zoned along with pitch-bend to affect only specific keys (unlike on the SY77)
Memory: 128 preset patches and 128 user patches, 16 preset multi-patch setups (up to 16 voices each) and 16 user multi-patches, 512 kB of RAM as standard for user-loaded AWM samples or MIDI data recording from/to connected devices
Expandability: 5 rear-mounted slots for SYEMB05 memory modules of 512 kB each, up to a total of 3 MB RAM with standard hardware. The final firmware revision, v1.57, supports up to 8 MB of total RAM, a capacity that so far has only been reached by Musitronics' now-defunct 5 MB upgrade board coupled with the full complement of 5 SYEMB05 modules (2.5 MB) and standard RAM (0.5 MB).
Control: MIDI in, out, and thru; pitch wheel; 2 modulation wheels; enhanced functions as a master keyboard when compared to the SY77, etc.