These are musical instruments.
“A magic harp is a tonal musical instrument, and one of the two harps. If it has any charges left...Magic harp
“There are two overall categories of musical instrument in NetHack: tonal instruments, which are...Musical instrument
“The Bell of Opening is a unique item you encounter during the Quest (along with your role's...Bell of Opening
“A horn of plenty is one of the magical horns, but unlike the other horns, it cannot be used as a...Horn of plenty
“A magic flute is a magical tonal instrument, and can be used to play the passtune. Improvising...Magic flute
“A bugle is a tonal musical instrument. It can be used to play the passtune to enter the castle...Bugle
“Some tools in this game are very rare. Some players may confuse the unidentified frost horn with...Frost horn