Willi Apel's classic study of Gregorian chant is now in paperback. This extensive survey describes the evolutionary processes of its long history as well as its definition and terminology, the structure of the liturgy, the texts, the notation, the rhythm, the tonality, and the methods and forms of psalmody.
Apel studied mathematics at the Universities of Bonn and Munich and the University of Berlin. Although pursuing mathematical studies, Apel continued to stud piano and gave music lessons.
Apel became a renowned musicologist and became a professor of musicology at Indiana University in 1950. He was awarded an honorary doctorate by the university in 1972.