Well, this is a question I hear often. And I suppose it’s reasonable, given a player knows and usually likes the sound of their instrument. And I’m about to do something - a repair, as setup adjustment, change something - that will change the way the instrument vibrates.

“Will it affect the sound?” Well, yes. Just about every change you make on an instrument will affect the sound in some way. Sometimes significantly, sometimes hardly at all, but everything has the potential to affect the sound. I can understand this is a scary prospect for as player.

However, I like to look at it this way; when a bass is in for repair or adjustment, this is usually to correct something already broken, faulty, worn, or a potential problem. Just this factor alone will also affect the sound, usually in a negative way. 

The work I will do, will result in an instrument that is intact, functioning, feels good and vibrates properly.  Yes, of course the work I do will affect the sound, but the effect of all the changes minor and major, will almost invariably be a positive result!