Multiphonics on vibrating strings have been an important element in my compositions since the early 1990s. In order to calculate the frequency components of so-called pure multiphonics (multiphonics consisting of harmonic partials of the fundamental) on vibrating strings, I developed my fraction windowing algorithm. The first section of this article details the use of multiphonics in my compositions and the second section discusses how the fraction windowing algorithm works and its relationship to the closely related mathematical concept of a continued fraction. The article also discusses the online apps I have developed as tools for composers and performers who are interested in using these methods in their own work on string multiphonics.