The Roland P-330 digital piano module was released in the late '80s shortly before the U-110. The U-110's accurate acoustic piano samples might explain why the P-330 wasn't very popular, but it might also be due to the flood of MKS-20s on the market after the U-110 was released. The P-330 attempts to do all the MKS-20 digital piano module can do, and more, all in a light weight one rack space package.
The P-330 is extremely similar to the MKS-20 featuring eight distinct digital tones: three pianos, two electric pianos, clavinet, vibraphone, and harpsichord. Unlike the MKS-20, any tone can be stored in the sixty four patch locations. User editable parameters include a two band EQ with parametric high and low, chorus type, depth, and speed, and vibrato type, depth, and speed. Chorus and vibrato on/off status can be stored with each patch, along with transposition. The P-330 sounds extremely similar to the MKS-20 piano module with only slight differences in velocity response between the two. The chorus has several waveform types, but doesn't quite have the thickness of the all-analog chorus of the MKS-20. Overall the P-330 makes an excellent light weight replacement for the MKS-20 at gigs, but I haven't given up my MKS-20s in my studio just yet.