The first movement of the “Jupiter” has been variously described, in three books of the 1980s, as full of the “spirit of comic opera,” as embodying a mixing of styles in “semiseria” fashion, and as being at once “monumental” and “saturated with the rhetoric that characterizes high comedy.” One key to understanding the multiplicity of expressive stances in this movement is the striking and persuasive idea of topics that has emerged from research into the period by Leonard Ratner and Wye J. Allanbrook: they argue that particular features of the music – rhythms, melodies, textures – represented familiar topoi, or topics, and that in this way Classical music was intelligible to its audience. These topics included dance types, with their characteristic meters and gestures (for example, minuets, sarabandes), rhythms (sometimes connected with dance, as in the march, or in unrelated categories, like alla zoppa), and references to other styles and genres (recitative, aria, French overture, hunt, fanfare, pastoral, among many others). Thus, the Classical composer may be seen as drawing on a common fund of musical types or “commonplaces,” the source of ideas and arguments that constitutes invention (inventio), the first of the five parts of Classical rhetoric. Composers and audiences invested these commonplaces with meaning.

On the face of it, this is an attractive way to “decode” the language of the late eighteenth century. The principal problems concern the identification and limits of topics within a piece: what is a topic and what is not? Is every tremolo passage in a minor key a “reference” to Sturm und Drang or every imitative passage “learned style?”