I recently acquired a semi hollow fretless bass, and I'm facing a issue with. Not sure if my guess is right, but due to the semi hollow nature of the instrument, the unplayed/unmuted open strings start to resonant, particularly when the volume gets higher. It's starting to prove quite annoying. Especially since its a 6 strings, I'm having to really go out of my way to thoroughly mute every unplayed string. I've been playing 6 strings for close to 10yrs, and non of my other basses have this issue. The bass has a brass nut, and I'm wondering if cutting a new nut with a softer material, like bone for e.g. would help ease down on the cross talk.