The whirly tube, corrugaphone, or bloogle resonator, also sold as Free-Ka in the 1960s-1970s, is an experimental musical instrument which consists of a corrugated (ribbed) plastic tube or hose (hollow flexible cylinder), open at both ends and possibly wider at one end (bell), the thinner of which is rotated in a circle to play. It may be a few feet long and about a few inches wide. The faster the toy is swung, the higher the pitch of the note it produces, and it produces discrete notes roughly belonging to the harmonic series, like a valveless brass instrument generates different modes of vibration. However, the first and the second modes, corresponding to the fundamental and the second harmonics, are reported as being difficult to excite.[1] To be played in concert the length of the tube must be trimmed to tune it.
According to the modified Hornbostel–Sachs organological system proposed by Roderic Knight[2] it should be numbered as "A21.31" (twirled version) and as "A21.32" (blown version), described as "a corrugated or ribbed tube that produces overtones through turbulence" . In spite of being an aerophone, it is usually included in the percussion section of "sound effects" instruments, such as chains, clappers, and thunder sheets.
- ^ Sprott, Julien Clinton (2006). Physics Demonstrations: A Sourcebook for Teachers of Physics, Volume 1, p.158. "You can also use a corrugated plastic tube, called a 'corrugaphone,' 'Bloogle Resonator,' or 'Hummer,' to produce a variety of whistling sounds when you spin it around over your head. The frequencies are harmonics of the fundamental organ-pipe mode that are individually preferentially excited depending on the speed of rotation. It is hard to excite the fundamental and even the second harmonic, but the higher harmonics are easily excited." ISBN 9780299215804.
- ^ Knight, Roderic (2017). "The KNIGHT-REVISION of HORNBOSTEL-SACHS: a new look at musical instrument classification" (PDF).