Unfortunately, Dom, I really don't know of any! I guess that was one of the major points in my skepticism of Ketron's claim. They can work pretty well offline, but when you use them in realtime. low latency streaming issues and the need to respond INSTANTLY to chord changes make all kinds of glitches appear. Of course, on a studio project, you don't HAVE to get glitch free on the live pass, because you can then render offline afterwards and get the perfect export.

Add to that that I really don't know of any guitar loop VSTi players that are NEARLY as comprehensive as an arranger player needs for the vastly different musics that arranger players from all over the world play, and I really don't see a comprehensive solution...

You see, the hiphop musician works with the loops he has, and creates music based around those. But arranger players tend to want to play stuff already composed, so the choices need to be comprehensive. Jazz playing, folk and alternative, latin, rock ska, ethnic... Just too many choices, IMO.

I don't honestly encourage you down this path. Firstly, I think it is going to be prohibitively expensive to produce the library (seeing as no-one makes one off the shelf), technologically difficult to implement in realtime, and as I have been saying for a while now, things like Roland's Guitar Mode (which will change guitar neck positions depending on how high up you play the trigger chord on the keyboard) and Korg's Guitar Mode (which DOES work in arranger mode), and the new dedicated guitar NTT's on the T3, coupled with detailed samples and the Mega Voice like muting and sample noises technology seems a FAR easier technology to implement and improve. And can sound, even with the low ROM sounds that ROMplers typically use, very realistic. I just think this technology, tied to the MS's ability to load MUCH, much larger sample sets (hence greater detail) is the better course.

Especially for a keyboard like yours, where you promote (almost insist!) that the owner customize the content, loops are just too hard to edit and customize, whereas MIDI files triggering Guitar Modes are as easy as altering a string line... I can't see someone picky enough to want an MS being content with a small, uneditable guitar loop library, unless their stylistic needs are quite narrow.

But there's ONE caveat... You will probably have to develop this yourself. Unfortunately, the sound, the technology to use that sound, and the data to play the sound are all inextricably linked. It's next to impossible to get Yamaha Mega Voice technology to trigger Korg DNC Guitar Mode voices and get an acceptable result (and vice versa) and Roland is another system altogether. This is just one of those things that have to all work together, it can't be cobbled together out of off the shelf parts.

I'm afraid there is no easy solution.

But you might at least check out Steinberg's Virtual Guitarist2 (although users report bugs), AAS's Strum (Mac only, though, I think) or MusicLab RealGuitar & RealStrat. Just don't expect great realtime performance...