Some lovely photos by Mierswa-Kluska of the interior of musical instruments made as part of an ad campaign for the Berlin Philharmonic. See them all.
I suspect the instruments were cleaned up a bit for the shoot. Old violins especially are notorious for collecting prodigious amounts of dust. Peter Seman (Seman Violins near Chicago) has a display case of musical curiosities that includes a large clump of dust retrieved from the interior of an instrument brought in for repair.