At just 34 years of age Théodore Dubois was installed as a professor of harmony at the Paris Conservatoire. Whilst much of his compositional works have disappeared from primary classical repertoire his teaching has had a lasting influence. Having taught successful composers including Paul Dukas it is clear that Dubois'' Treaty of Harmony is well-informed. This music theory study guide covers a considerable range of theoretical aspects from the varying musical clefs to the use of pedal notes as well many other harmonic devices with expertise. During the preface Dubois explains the need for hisbook stating that it fills the gaps in harmonic theory exercises which preceding guides had missed. With no harmonic elements left out this Théodore Dubois theory guide is necessary to accompany all music studies.