Harry Partch (June 24, 1901 - September 3, 1974) was an American composer, music theorist, and creator of musical instruments. He composed using scales of unequal intervals in just intonation, and was one of the first 20th-century composers in the West to work systematically with microtonal scales. He built custom-made instruments in these tunings on which to play his compositions, and described his theory and practice in his book Genesis of a Music (1947). Partch composed with scales dividing the octave into 43 unequal tones derived from the natural harmonic series; these scales allowed for more tones of smaller intervals than in standard Western tuning, which uses twelve equal intervals to the octave.

Partch made public his theories in his book Genesis of a Music (1947). He opens the book with an overview of music history, and argues that Western music began to suffer from the time of Bach, after which twelve-tone equal temperament was adopted to the exclusion of other tuning systems, and abstract, instrumental music became the norm. Partch sought to bring vocal music back to prominence, and adopted tunings and scales he believed more suitable to singing.  Inspired by Sensations of Tone, Hermann von Helmholtz's book on acoustics and the perception of sound, Partch based his music strictly on just intonation. He tuned his instruments using the overtone series, and extended it past the twelfth partial. This allowed for a larger number of smaller, unequal intervals than found in the Western classical music tradition's twelve-tone equal temperament. Partch's tuning is often classed as microtonality, as it allowed for intervals smaller than 100 cents, though Partch did not conceive his tuning in such a context. Instead, he saw it as a return to pre-Classical Western musical roots, in particular to the music of the ancient Greeks. By taking the principles he found in Helmholtz's book, he expanded his tuning system until it allowed for a division of the octave into 43 tones based on ratios of small integers.  Partch uses the terms Otonality and Utonality to describe chords whose pitch classes are the harmonics or subharmonics of a given fixed tone. These six-tone chords function in Partch's music much the same that the three-tone major and minor chords (or triads) do in classical music. The Otonalities are derived from the overtone series, and the Utonalities from the undertone series. Answer this question using a quote from the following article:

What is the Theory ?
Western music began to suffer from the time of Bach,