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Description

The Pentachord is a type of "long string instrument." These types of instruments have been created by various composers and instrument builders in order to perform music written in Just Intonation (a tuning system where every pitch is a whole number multiple of a fundamental frequency). This particular instrument is modeled after the two string version created by Daniel Schmidt. Different pitches are produced by touching a string at various nodes which are whole number divisions of the string length (ex. ½, 1/3, ¼, etc...) while bowing it. This is exactly the same as playing only natural harmonics on any traditional string instrument.

The advantage of the strings being so long is that it allows you to more easily produce higher harmonics than shorter instruments. For example, a violin can typically only achieve up to the fifth harmonic (five times the open string frequency) where as a long string instrument can easily produce anywhere between the twelfth up to the twentieth harmonic depending on its length. Natural harmonics are, by definition, perfectly in tune in Just Intonation but are rarely in tune with equal temperament so while these instruments are not suited to playing traditional western music, they are perfectly suited to anything based in Just Intonation.

The Pentachord, which means five strings, has five strings (obviously) but the name also refers to how the strings are tuned. We describe all western scales as being built from two tetra chords (a four note grouping where each note is no more than a step away). The first notes of each tetra chord in a scale typically make a perfect fifth (Do, Sol). I decided to extend this idea to having five notes in the space of the four typically used to divide the fifth (which is also the interval between the second and third harmonics). The result is that each string is higher or lower than its neighbor by less than a whole step but more than a half step. In order to keep the distance between strings in Just Intonation as well, the tuning difference is also a whole number ratio that results in this distance being achieved. The musical result is that the instrument can produce various scales which have nine notes to the octave (rather than the traditional seven) with a tremendous amount of microtonal variation possibilities as you move to higher harmonics.

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Works for the Pentachord

-Pulses (2009 by Cole D. Ingraham) for Bonang Pelog, Electric Guitar, Pentachord, and Contrabass

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