Partch first presents a polemic against both equal temperament and the long history of stagnation in the teaching of music; according to Alex Ross, this is "the most startling forty-five-page history of music ever written". In particular, Partch holds Johann Sebastian Bach responsible for "the movement toward equal-tempered tuning, which meant that composers could not absorb the scales of other world traditions; and the urge to make music ever more instrumental and abstract."
He then goes on to explain his tuning theory based on just intonation, the ensemble of musical instruments of his own invention (such as the "Surrogate Kithara, a struck-string, harplike instrument", and the guitar with movable frets he used to compose Barstow), and several of his largest musical compositions.
The book has been highly influential to succeeding generations of microtonal composers, including Lou Harrison, Ben Johnston, and James Tenney. A revised and enlarged second edition was published just before Partch's death in 1974.
Partch presents 4 "basic monophonic concepts":