Quadrangularis Reversum

The American composer Harry Partch composed using scales of unequal intervals in just intonation, derived from the natural Harmonic series; these scales allowed for more tones of smaller intervals than in the standard Western tuning, which uses twelve equal intervals. One of Partch's scales has 43 tones to the octave. To play this music, he built a large number of unique instruments, with names such as the Chromelodeon, the Quadrangularis Reversum, and the Zymo-Xyl.

Partch called himself "a philosophic music-man seduced into carpentry". The path towards Partch's use of a large number of unique instruments was a gradual one. Partch began in the 1920s using traditional instruments, and wrote a string quartet in just intonation (now lost). He had his first specialized instrument built for him in 1930—the Adapted Viola, a viola with a cello's neck fitted on it.

He re-tuned the reeds of several reed organs and labeled the keys with a color code. The first one was called the Ptolemy, in tribute to the ancient music theorist Claudius Ptolemaeus, whose musical scales included ratios of the 11-limit, as Partch's did. The others were called Chromelodeons, a portmanteau of chrome (meaning "color") and melodeon.

Most of Partch's works used the instruments he created exclusively. Some works made use of unaltered standard instruments such as oboe, clarinet, or cello, and Revelation in the Courtyard Park (1960) used an unaltered small wind band.

In 1991, Dean Drummond became the custodian of the original Harry Partch instrument collection until his death in 2013. In 1999 the instruments began a residency at Montclair State University in Montclair, New Jersey which lasted until November 2014 when they moved to University of Washington in Seattle. They are currently under the care of Charles Corey.

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