Each tube of a panpipe is closed at the bottom and open at the top. The longer the tube, the lower and deeper the note. So a row of different-sized tubes gives you a whole scale of notes - low ones on one side, high ones on the other. The bigger the panpipe, the deeper the sound.
Andean musicians often play in pairs. One musician has the odd-numbered notes; the other has the even-numbered notes. To play a tune, they take turns - back and forth - blowing their own notes at exactly the right moment. It only works if they listen carefully to each other.
The panpipes are often played together with a small wooden drum called a bombo, and a tiny stringed instrument that looks like a half-sized guitar called a charango. Together they make the soft, soaring sound that Peruvian and Bolivian mountain music is famous for.
You can make a simple set of panpipes from drinking straws. Cut several straws to slightly different lengths, tape them in a row, and blow gently across the top. The longer ones sound deeper. It is one of the simplest instruments humans have ever invented - and one of the oldest.