The DS-250 was an electronic keyboard manufactured in 1985[3] by Seiko and was considered a commercial failure.
[6] The unit used additive synthesis for sound generation, chorus and ports included MIDI[2] In, Out and Through, RCA outputs (stereo), Headphones and level controls for both channels.
[2] It is capable of running either a single sound or two sounds at once, either layered or split, and each of these can be used on its own MIDI channel (there are small dials on the end of the keyboard to set each channel).
You can change the detune and pitch intervals between the two layered sounds.
[1] It had four buttons Record, play, stop and pause, a tempo slider.