The Kawai K4 is a 61 key synthesizer manufactured in 1989 by Kawai. It contains several features beyond those offered on Kawai K1, adding resonant filters and a DAC PCM wavetable. The K4 incorporated a new type of synthesis called Digital Multi Spectrum.
Interestingly, the K4 uses a system that splits 16 bit samples between two read only memory (ROM) chips, while reserving a third chip for 8 bit sound samples that naturally have more noise (such as cymbals, snares, and other noisier percussion) in order to have more functionality for a cheaper manufacturing cost.
A 2U rack mounted module was also produced by Kawai. It has six separate audio outputs in addition to standard left/right stereo outs and a headphone socket. The effects are removed in the rack mounted version as it is presumed outboard effects will be used with the unit.