Using the Casio CT-X5000 as the controller, with the sound on, playing a MIDI connected Juno DS 61, with it's sound on, you get something neither can do on it's own. The Casio handles the accompaniment and one layer of the lead part, the Juno DS plays the same parts, except the lead instrument is different. Yes, playing a layered sound over MIDI, with the accompaniment part playing on both keyboards.