It is generally thought that, except for a few pieces with specifically notated quartertones, the remainder of Ives’s music was conceived for conventional twelve-tone equal temperament. However, there’s a great deal of evidence in Ives’s scores and writings suggesting a general tuning for his music that can best be described as Extended Pythagorean.

Ives wrote that the themes and general plan for the Universe Symphony are quite clearly indicated in the sketches he left behind. But deciphering those sketches has been one of American music’s greatest detective sagas.