Cat Stevens - Numbers. Notably - Art Garfunkel sings on this record, and David Sanborn gets a sax credit.
This is from wiki: "Numbers is concept album by singer/songwriter Cat Stevens released in November 1975. Subtitled "A Pythagorean Theory Tale", it is a concept album based on a fictional planet in a far-off galaxy named Polygor and the "Polygons" who inhabit its palace. The album includes a booklet (which was in the used album I bought recently! you can see that in the photo above...) with excerpts from the planned book of the same name, written by Chris Bryant and Allan Scott, and contains pen-and-ink illustrations by Stevens.
The idea shaped into a fantastic, spiritual musical set on the planet Polygor. In the story, there is a castle with a number machine. This machine exists to fulfill the sole purpose of the planet: to disperse numbers to the rest of the universe—1, 2, 3, 4, 5, 6, 7, 8, and 9 (but notably, not 0). The nine inhabitants of Polygor, called "Polygons", are Monad, Dupey, Trezlar, Cubis, Qizlo, Hexidor, Septo, Octav, and Novim. As the last lines of the book say, they "followed a life of routine that had existed for as long as any could remember. ... It was, therefore, all the more shocking when on an ordinary day things first started to go wrong." The change takes the form of Jzero, who comes from nowhere as a slave and eventually confuses everybody with his simple truth.