Subtitled "A Pythagorean Theory Tale," Numbers was a concept album relating to a faraway galaxy, a planet called Polygor, a palace, and its people, the Polygons. So one learned from the album's accompanying booklet. The songs presumably told the tale, but as with so many concept albums, listening to Numbers was like hearing a Broadway cast album without having seen the show — something seemed to be going on, but it was hard to tell what. The setting did allow Cat Stevens to indulge his affection for Middle Ages madrigal music, and individual songs, notably the singles-chart entry "Banapple Gas," were appealing. The lyrics were full of references to home, God, and "the truth," which gave the whole a vaguely spiritual tone, though the key word here is "vague." Stevens fans may have been somewhat put off by the fear that Numbers was a kind of musical math class — though it went gold, the album was the first in his last seven to peak below the Top Ten.