Korg is kinda on track with this.. Look at what you can do with the M3... These synths let you mount the Radias R..., and I think the 88 key version allows you to mount both the Radias R.., and a second M3 Module... A very cool thing to look to in the future if you don't want to dish out more dough for a full keyboard.
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GEAR: Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller). SOFTWARE: Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.