Dear Guest Richie,

What I believe you must do is to coax this particular mouse out as the scraping is more than likely due to a hairy ball. I agree with you entirely, the inside of a guitar is indeed like a parallel universe and it may be difficult to find your mouse there. One possible solution may be to procure a woodworm and cause it to produce a wormhole into this alternative universe. This will enable your trapped mouse to escape back into this universe.

Once thus retrieved, your hairy mouse may be treated humanely (I can do this for you for a small fee) and replaced by a cordless optical mouse. This mouse has no moving parts to cause those annoying scraping noises nor any trailing cord to become entangled in your strings. I believe this will provide a permanent solution to your problem.

P.S. The wormhole will require to be closed after treatment to prevent the sucking in disappearance of any other IT equipment, household items, pets or loved ones into the vast emptiness that is the parallel universe of the guitar's interior.

Yours sincerely,

Dr. Guitar