In June 1791, having composed almost no church music for ten years, Mozart wrote the short motet Ave verum corpus, k618, a setting of the Latin medieval eucharist hymn. The theological teleology in the text introduces a process-like aiming at a goal that cannot, however, be reached. This study is about how teleology operates in the motet – the ways in which the text's ultimately unfulfilled goal-directed processes operate in Mozart's music. The music is approached from a variety of analytical perspectives that reflect different aspects of this theme: the new Formenlehre and phrase structure, topic theory, and the analysis of voice-leading structure, register and hypermetre. Together, these approaches elucidate the multiplicity of musical processes that, as in the motet's text, announce a goal but fail to reach it.

The long careers of Carl Philipp Emanuel Bach and Joseph Haydn coincided with fundamental transformations in how keyboard instruments were built and played and how composers wrote for them. Haydn's keyboard music probably saw the more profound changes in compositional style, yet C. P. E. Bach and others preceded him in discovering ways to incorporate new keyboard idioms into pieces written for new types of instruments. Bach gradually shifted from writing generic keyboard music to composing in idioms most appropriate to two-manual harpsichords, unfretted clavichords or fortepianos. Haydn likewise began writing in a generic idiom; many works that have been posited as having been meant for the clavichord cannot in fact be assigned clearly to that or any other specific instrument. Although Haydn did eventually turn to writing specifically for the fortepiano, he too made a gradual, and relatively late, transition from a generic approach to one that centred on the grand fortepianos of the late eighteenth century. Bach's influence on Haydn is inseparable from the matter of the keyboard instruments. Although the precise nature and extent of Bach's influence cannot be determined, compositional elements derived by Haydn from Bach's music range from superficial thematic and notational parallelisms to fundamental conceptions of what keyboard music could be or could express.