Hmm, that may sound like a silly idea, but I have been wondering while practicing fretless bass (without looking at the neck) if some form of subtle tactile reference points or grooves could be put on the back of the neck?

Anyone tried something like that?

Sounds like a cool idea! I've seen brass nails (small, maybe 3/8" long, called escutcheon pins) with nice rounded, almost semi-spherical heads. I can imagine a row of of them, properly positioned, on the back of the neck- fretless meets braille!

Thats a really cool thought. Theoretically I think its a great idea but practically I think it gets a little complicated. I really good system would have to be worked out because think how confusing it would get when you get up farther up the neck. At the 24 fret they would be all mashed together. But then again people can also slide from like the 12 to 24 fret just by the feel and knowing their basses. So maybe it could work.

I put some pieces of thin pin-stripe tape on the back of the neck to try the idea. It does work, sort of. One problem is thumb position, my thumb is *almost* underneath the middle finger, but not quite. So some adjustment have to be made to feel the line. Another problem is overall feeling of the back of the neck, the lines are good as a reference, but a smooth neck feels better. Perhaps thin grooves (2/3 inches wide or so across the middle of neck?) would be better.

Maybe, maybe not. :)

You could put longer lines or grooves, or double nailheads, at positions 3, 5, 7, 9, 12, 15, 17, 19, 24, etc.

Maybe the best places for the lines would be the underside of the neck near the edge of the fretboard, so you could feel them with the fretting finger instead of the thumb ... just an idea.