Marion. There are products sometimes available from paint suppliers, sometimes called gloss busters. They are made to do exactly what you are asking for, to give a very slightly roughened surface. This is in preparation for painting, of course.
The stuff is like domestic cleaning paste (Ajax creme?) but has a finer grain size from the feel of it, more like the abrasive in toothpaste.

You could try it, if you are feeling brave. Sparingly, and starting where it can't be seen, and washing off the residue as you go, so that you can see what (damage) you are doing.

You could even try toothpaste! The abrasive in that is rumoured to be powdered nut-shells.

BUT! Very gently, and entirely at your own risk. I like glossy instruments anyway.
Do keep us informed.