We don't have synonyms for pan pipes yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are panpipe, pan pipe and pan-pipes.
(n) :
Alternative form of panpipes. [(music) An instrument consisting of a series of ten or more tubes of different lengths, typically closed at the bottom and open at the top, and is played by blowing across the open end at the top.]
(n) :
Alternative form of panpipes. [(music) An instrument consisting of a series of ten or more tubes of different lengths, typically closed at the bottom and open at the top, and is played by blowing across the open end at the top.]