Generally in fair condition. Some small marks to the keys, rear sticker peeling off. Working well but shows "Warning: Change Wav BAT! INT" message on start up, which vanishes after pressing exit. Numerous scratches to base, as it was used in a musical production and so was on and off stands consistently. Scratches to edges. Top side is decent as per photos. Please study photos for condition information carefully. Keys appear yellower in pictures than in reality. We believe the keyboard has been modified to run off a simple UK kettle lead, and seems to work well on this basis. 

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 SPX50 or SPX90), and several other enhanced features.

• Date produced: 1991
• Polyphony: 16 notes ("Elements") of AFM + 16 notes (Elements") of sample-playback (AWM2)
• Voice Architecture: Each voice can have up to 2 AFM (6-operator) Elements polyphonically, or 4 AFM (6-op) Elements monophonically, plus up to 2 AWM Elements
• Filter: 2 multi-stage, time-variant, with resonance and self-oscillation per Element
• 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, 512kB 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 512kB each, up to a total of 3MB RAM with standard hardware. The final firmware revision, v1.57, supports up to 8MB of total RAM, a capacity that so far has only been reached by Musitronics' now-discontinued 5 MB upgrade board coupled with the full complement of 5 SYEMB05 modules (2.5MB) and standard RAM (0.5MB).
• Control: MIDI in, out, and thru; pitch wheel; 2 modulation wheels; enhanced functions as a master keyboard when compared to the SY77, etc.