While many new interfaces for musical expression have been presented in the past, methods to evaluate these interfaces are rare.This paper presents a method and a study comparing the potentialfor musical expression of different string-instrument based musicalinterfaces. Cues for musical expression are defined based on results of research in musical expression and on methods for musicaleducation in instrumental pedagogy. Interfaces are evaluated according to how well they are estimated to allow players making useof their existing technique for the creation of expressive music.