Branching Corrugahorn

Last modified 8-12-2009

Here’s an instrument that only came into existence because 20th century industrial production created the essential material. The essential material is a flex tube of the sort made with a ridged or corrugated surface. When you blow air through a corrugated tube, the air sets up a standing wave as it bumps over the ridges, and you hear a clear tone. The harder you blow (that is, the faster the air rushes through) the higher the tone — except that the tone does not glide upward like a slide whistle as the air speed increases; instead it jumps from one discrete pitch to the next higher within the harmonic overtone series of the tube length.

Branching Corrugahorn

Branching Corrugahorn

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Excerpt from “Branching,” played on┬áthe Branching Corrugahorn

In the instruments you see here, several corrugated tubes of different lengths are fed by a single mouth-blown air chamber. Each tube provides several notes but not a complete scale. Between the several of them, the complete scale becomes available. In playing the instrument, you stop the ends of the tubes that you don’t wish to sound at any given moment with fingertips, and lift the finger to allow air through whichever tube you wish to sound.

This is one of the instruments featured in the CD Instrumentarium Hopkinis: Bart Hopkin Plays Invented Instruments. You can hear a short excerpt featuring the Branching Corrugahorn by clicking the sound link above.

More complete descriptions of this and other corrugaphonic instruments have appeared articles in Experimental Musical Instruments quarterly journal. Volume 5 #3 (Oct 1989) contained a piece from Sarah Hopkins on her use of the larger whirled corrugated plastic tubes, and one from physicist Frank Crawford describing the acoustics of such instruments. In an article in Volume 6 #5, Bart Hopkin described the instruments pictured here in more detail, and went on to various other corrugophonic possibilities.

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