Rhythmicana

Henry Cowell's 1938 work Rhythmicana is a suite of piano pieces centered on polyrhythms and dissonant counterpoint. It is known for its unusual time signatures, with the first two movements being in time, and the third movement having the polymeter of  in the right hand and  in the left.

Background
Cowell had already used the title for his rhythmicon concerto seven years earlier. The complexity results from Cowell's lifelong preoccupation with rhythmic exploration. The piece is dedicated to J. M. Beyer.