 Decomplex actions draw on different kinds of complex movements, involving the association of movements with perceptions in one or more sensory modalities: at the sight of the notes on the staff, or the sound of the tones, the pianist hits the keys. As a person becomes proficient at a type of decomplex action, the guiding sensory modality can change. When learning to dance, Hartley observes, at first “the scholar desires to look at his feet and legs, in order to judge by seeing when they are in a proper position,” but “by degrees he learns to judge of this by feeling” (OM 1, prop. 77). Similarly, a practiced musician plays the harpsichord from “the connexion of the several complex parts of the decomplex motions” (OM 1, prop. 21). One’s hands know the tune.