This paper is addressed to teachers, rather than to artists. In it I present to you a summary of Lussy's Treatise on Musical Expression—a work published in Paris in 1874, and now in its second edition. I know nothing of the author beyond his own statement, that for twenty years he has been a professor of the pianoforte in Paris. His work is dedicated to M. Gevaert, principal of the Brussels Conservatoire, ‘who,’ says the author, ‘when illustrious theorists and composers declared that a treatise on expression was impossible, encouraged me to proceed and gave me valuable advice.’ Musical people all shake their heads at the notion of reducing to rule such an intangible thing as expression. As well, they will say, might we show a person how to love, as how to impart feeling to what he plays. Of course there is much truth in this, but let us try for the moment to allay our prejudices, and hear what M. Lussy has to say.