short flute with stopped lower end and flue that directs player's breath from mouth hole at upper end against edge of hole cut in whistle wall, causing enclosed air to vibrate; sounds only one pitch; has no finger holes; may have pellet enclosed—as in police whistle—causing warbling sound; sliding whistle (piston flute or Swanee whistle) has sliding stopper at lower end, allowing change of pitch; whistles originally made in preliterate societies from bird bones and used primarily to make music; used in modern societies primarily for signaling; considered oldest flute known.