DigitalNeohuman | Pyrotechnic Circus Medley Music Accompanying Set Pieces @DigitalNeohuman | Uploaded September 2010 | Updated October 2024, 3 minutes ago.
The Western Pennsylvania Skylighters presentation of Music with Pyrotechnic Whistles at the 1997 Pyrotechnics Guild International convention in Amana, IA.

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From the Journal of Pyrotechnics website:

Whistle tubes of various diameters and lengths are used to produce individual notes. The tubes, containing small amounts of compressed whistle composition, are fired electrically.