The Kawai K4r is the rack-mount sibling of the K4 keyboard and it has all the features of the keyboard version except for the effect processor section (and the keyboard itself, as you might have guessed). Instead it has eight individual outputs.

The K4r resembles in many ways the Kawai K1 synthesizer - it also uses preset PCM samples of acoustic instruments as a base for its sounds. The biggest difference is an added filter section.

In Multi-mode, the synth works as a great multi-timbral sound module - you can stack voices on top of each other as you wish, let them overlap, split or use velocity to switch between them. Unfortunately the underpowered processor which sometimes makes the K1 behave strangely, seems to have been used in the K4 as well. This is particularly noticeable when you start stacking sounds or let the K4 play on many MIDI channels at once - strange MIDI delays and a general, unpleasant "looseness" will begin to occur.

The sound of the K4 has a special "grungy" character of its own. It does weird and "industrial" noises quite well.