Musical instruments ground players’ actions and the sounds they create. Yet this book further claims that instruments mediate perception and imagination. Practicing an instrument builds bodily skills, while also fostering auditory-motor connections in players’ brains. These intersensory links reflect the ways that a particular instrument converts action into sound, the ways that it coordinates tonal and physical space. Reactivated in various ways, these connections can influence instrumentalists’ listening, improvisation, and composition. To investigate these effects, the book engages both classical and popular styles, from Bach to electronic music, from Beethoven to the blues. It uses Lewinian transformational theory to model instrumental interfaces and to analyze patterns of body-instrument interaction. Though based in music theory and analysis, the book also draws on psychology, including cognitive neuroscience, and the phenomenological philosophy of Maurice Merleau-Ponty and Martin Heidegger. Ultimately, it argues that music cognition is not simply embodied; it is also conditioned by musical technology.