Yamaha's SK-series are combo-keyboards with synthesizer, organ, brass and string sections. The SK 10 was the first of the SK-series, released in 1979. The SK 20, SK 30 and 50D followed in 1980, and the SK-15 in 1981.
"The Yamaha SK 50D Symphonic Ensemble effectively unites organ, strings, polyphonic synthesizer, solo synthesizer and bass in one great instrument, providing endless combinations of sounds with the versatility of control by two 61-key keyboards. This give the multi-keyboardist access to the sounds that previously required server keyboards - all in one portable instrument."
"The SK 50D organ section features a full range of stop levers from 1' to 16', percussion levers for 2nd, 3rd and 5th harmonics and controls for overall sustain, brilliance and decay. In addition to the manual organ sound controls, three preset voice buttons are provided for the upper keyboard and two for the lower keyboard." (Yamaha Catalog)
"The Poly-Synth is a 7-note polyphonic synthesizer with complete control and pitch, filter cutoff and resonance, envelope generator depth, a full ADSR, as well as sustain, slow attack and brilliance functions. Six preset selectors are provided in the poly-synth section, three for preset poly-synth voices, three for strings.
The solo synthesizer section is a monophonic synthesizer featuring a VCO, VCF, VCA, EG and LFO.
The SK 50D is equipped with an exclusive bass section that offers 16', 8' and attack 8' stop levers, as well as sustain and brilliance controls. It can be played either via the manual bass area of the lower keyboard or an optional bass pedal unit (BP-2)
In addition to the effects provided in the solo synthesizer, the SK 50D offers ensemble, tremolo and delay vibrato. Foot control capability is extensive with jacks for mixed, poly-synth and strings volume pedal, and footswitches for sustain and portamento control. An external tone cabinet connector permits connection to a rotating speaker unit." (Yamaha Catalog)
