Piped music (5)
'piped music' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for pibroch that I've seen before include "Theme and variations on bagpipes" , "piece of pipe music" , "Tune" , "Classical music of the bagpipe" , "Piped music" .)
(Other definitions for muzak that I've seen before include "Background music played in public places" , "Notes for public places?" , "Piped shopping mall "entertainment"" , "Lift notes, perhaps" , "sequence of notes all over the place?" .)