Complex sentence: The oldest phase at Jiahu only contains two flutes, which are tetratonic and pentatonic; the middle phase at Jiahu contains several flutes, including an interesting pair of hexatonic flutes.
Split into simpler sentences: The oldest phase at Jiahu only contains two flutes, which are tetratonic and pentatonic. The middle phase at Jiahu contains several flutes, including an interesting pair of hexatonic flutes.