This MKS-10 is fully functional and in great condition.
The MKS-10 Planet-P is a 16-voice polyphonic piano sound module with MIDI, released in 1984 by Roland. It has just eight preset sounds: two Piano sounds, two Clavi sounds, two Harpsichord sounds, and two Electric Piano sounds. The sounds can be freely combined and stored in any one of the 128 memory patches.
Sounds can be tweaked, but only slightly. There is a Brilliance control to adjust the brightness of the sound, and short and long release time settings. Chorus, Flanging and two different Tremolo effects are also provided. The effects can be adjusted using the Rate and Depth controls. All effects, filter and envelope settings are also stored into patch memory. There are also master Tune and Volume controls on the front panel. The MKS-10 can respond to MIDI velocity as well as MIDI control change messages for expressive playing and realtime tweaking via your MIDI keyboard controller or sequencer.
The MKS-10 is an analog instrument, however for a Piano sound module, its sounds really are not that great nor realistic. Although it supported 16 MIDI channels, it is monotimbral and can only actually play sounds on one channel at a time. The MKS-10 was replaced by the MKS-20, a digital Piano sound module based off the Roland RD-1000.