A unit used in music to describe the ratio in frequency between notes. The quarter tone, equal to 1/24octave, is the basic interval in a 24-tone scale. Two notes differ by a quarter tone if the ratio in their frequencies is 21/24= 1.0293
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}