5. An instrument as claimed in claim 1 wherein the output device comprises a store storing therein at least one signal set representing the known or predetermined rhythm, a comparator for comparing the input signals with at least one stored signal set, and signaling means indicating a relationship between the rhythms represented by the input signals and the stored signal set.
5. An instrument as claimed in claim 1 wherein the output device comprises a store storing therein at least one signal set representing the known or predetermined rhythm, a comparator for comparing the input signals with at least one stored signal set, and signaling means indicating a relationship between the rhythms represented by the input signals and the stored signal set. 8. An instrument as claimed in claim 5 wherein the output device is selectively operable to provide at least one of a visual and an aural representation of the stored signal set or the selected signal set.