This is some cheap digital piano workstation made by Yamaha in the 1990s. It's a ROM-pler in that it's a "synth" that plays back samples in ROM when you press the keys. It allows for little to no control over the waveforms within the unit. The piano sounds are alright. The keys are kind of crap, in that they are sticky. Nothing a good cleaning wouldn't fix. It is used as a general MIDI controller for the computer music workstation. The unit also supports General MIDI so it can be an lol device for downloaded .mid files for karaoke!!! It has built in speakers and a 1/4" TRS headphone output. If there is a cable or adapter in the headphone plug, it kills the internal speakers with some kind of mechanical switch. There are 1/4" unbalanced aux outs to record the fine quality built in sounds.
It has a built in sequencer and a metronome, though the author can't figure out how to configure these for odd numbered time divisions, like 3/4. So it's kind of garbage. The sequencer can record and play back multiple tracks. There is a floppy drive inside the unit to store sequences, but the motor is broken so it's just a fancy drink holder now.