I plan to be very generous in my definition of “flute” and “pipe” here. You may see me use the terms interchangeably.
I’m interested in flutes, pipes, recorders, whistles, ocarinas, and all their variations world-wide. There are a lot of variations.
Some of these instruments make sound when the player breaths directly into the mouthpiece, like a recorder. Others work when the player blows across a hole in the tube, like on a Western, classical flute.
There’s always at least one tube (or sphere) and a player who uses his or her breath to make music. I’ve heard a beautiful sound come from a PVC pipe-turned-flute.