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My percussion quartet Locomotion calls for nine boos, which are wooden tongue drums.
See Musical Instrument Design: Practical Information for Instrument Making by Bart Hopkin for information on the construction of boos. Quoting Hopkin, "Boos are an important variation on tongue drums. Harry Partch gave the name boos to a set of vibrating tongue instruments he made of bamboo; I am taking the liberty here of expanding the term to include a host of similar instruments made from other materials."
Construct the boos in the form of rectangular wooden boxes that are closed at one end and open at the other, and with a tongue cut in the open end. The following example illustrates the procedure.
Ad Astra Percussion: Von Hansen performs a drag stroke on the boos
at the very end of Sleep Walk (Locomotion, movement 2)
My boos: 38, 32, 26, 22, 18, 15, 12, 10 and 8 inches in length
Approximate pitches: F2, A2, B2, D3, F3, G3, Bb3, D4, E4
Locomotion does not call for specific boo pitches, though the pitch range given above (E2 - E4) is recommended. If you would like to create boos with specific pitches, the following information can be used. Note that this is approximate and will likely only get you within a half step of your desired pitch.
A boo is a rectangular box closed on one end and is similar acoustically to a cylinder closed on one end. A closed cylinder has resonances approximately at the following frequencies:
frequency = n x speed of sound / (4 x length) for n = odd integers (1, 3, 5...)
or more accurately:
frequency = n x speed of sound / (4 x (length + .4 x diameter)) for n = 1, 3, 5...
Solving for the length, and using n = 1 for the fundamental frequency:
length = (speed of sound / (4 x frequency)) - .4 x diameter
Using 13,512 inches/second for the speed of sound and 6 inches as an approximate diameter (based on using wood that is 1"x6" for the sides and 1"x8" for the top and bottom), the length of a boo can be calculated as a function of the desired frequency.
More information is at Wikipedia.