Thanks a lot for the responses regarding the center detent for the minimoog.
I think that's done with two diodes in parallel, but opposite directions. Also you need to route a -10v feed to the wheel if I recall. Looks a simple mod, though I've never done it.
I finally did the mod. Had to wait for my parts supplier to find the right precision resistors (332k - fairly odd). Quite easy to do the mod.
It did make the center detent a notion wider, Not much, rather subtle change, actually, but probably enough for a performer to notice.
The mod is also said to improve on VCO stability, and I did actually notice that. Probably subtle that too, being an early minimoog with the early VCO card so it is probably drifting a little anyway.
I am happy with the mod, and I hope my client is too.
Thanks a lot for all the feedback on this.