Actually using a VSTi with vvArranger will work quite seamlessly..I was doing it

The BIG problem with the MS - well two really, was Linux was a piss-poor OS for running audio apps, (still is!!!) apart form DJ tasks, and Dom wasted ALL that time trying to adapt an engine (the elastique I think it was) to have styles using all audio..As Ketron have found out to their loss it is a LOT harder than you think - you know this...

vArranger is much the same as Karma in that ALL it generates is MIDI data...what you send that midi data to is up to the end user..

I actually had it running okay with the TTS-1 synth loaded up in Sonar (TTS-1 is the Roland Sand Canvas VSTi included with Sonar, and it is 16 part multi-timbral) sound was average, but it worked okay using a software midi router...

If I was sticking with the laptop method, I would set up templates in Sonar with various vst's racked to take the midi data from vArranger...for each of the parts..that is if I was not happy with the Ketron Sd2, or 4.

I had already got this software vst hookup working with the now defunct OSL Rack Project...

But there is no way in the foreseeable future imo that hardware arrangers are going to get replaced by software - it is all just a bit clunky and awkward, achievable, certainly, sounding good, yes -but jst too many hoops to get through.