Hm... guess I'll take a lucky shot at a Behringer BSY600 for 40€ and see how that turns out to be when used with a guitar.
I know that most people don't like the Behringer brand, but I have a US600 (Harmonizer - third up) and a RV600 (Shimmer) and both work just fine for me despite mixed reviews on HC. Guess I'll give the BSY600 a chance. If it all goes wrong I can still sell it used for 20 bucks. Nothing much to lose on that.
Thank you very much. You've been most kind and informative.
Alex
'course, being rehearsals, it couldn't simply have been a whim thing and just trying something different for the hell of it.