The K4 effects processor included chorus, reverb, distortion, delay and a flanger.
The rackmount version K4r includes eight outputs and has all the same features except for the effects processor. Besides that, it was very similar to the K1 with a 61 note keyboard that had velocity and aftertouch, 16 voices and 8-part multitimbral. It also included a digital resonant filter which greatly expanded the variety of sounds that could be programmed. It was improved over the K1 series with a much better acoustic piano sound, better synth waves and was not as 'noisy' as the K1. Kawai released the K4 in 1990 as their followup to the K1 series synths.
