Section dedicated to the Kawai K4 Synthesiser. so what is the K4? Well The K4 from Kawai is a warm and fuzzy digital synth. A sample-based digital synth, PCM and 16 Bit, featuring a Digital Filter unlike the K1. The K4 also comes in as a Module the K4R and features 8 individual Outputs but no Effects like its fully keyed bigger brother.