I am quoting a past post by synerjim.

"I'm a minimalist, so my setup is composed only of MJPro or coming SD40, Korg Microkey 61, Headset Mic and a Bose L1 Compact or Aiwa EXOS-9."

Just an SD40 or MJPro with the Microkey 61 is indeed a very minimal setup. I wonder if Ketron ironed out all the bugs in the SD40 that some mentioned about. I like the idea of an arranger module whether it is hardware or software such as vArranger. You can use any size keyboard. Flexible. I have Microkey 37 and 61. Just ordered the Bluetooth version Air 61 to play vArranger wirelessly.