This is Volume XVIII of twenty-one of collection of works on Cognitive Psychology. Initially published in 1927 it offers a collection of essays on the effects of music on the listerner.The book is at once a response and a challenge. It is a response to the inquiry which any thoughtful listener makes, “ What is this music doing to me ? ” A t the same time it is a challenge to science to explain more adequately than has as yet been done the nature and the mysteries of musical effects.