Harmony in the Classical era

The Classical era inherited the structure of homophony, or melody + accompaniment, from the Baroque era, but instead of the ornaments and profusion of the Baroque, the goal was now to achieve a systematic, natural and simple expression in both the melodic lines and in the harmonies underpinning them. For the first time in the history of music, theoretical rules prescribed how harmonies should progress, and the functional harmony of tonality was established. Composers either followed these rules or, somewhat later, began to break them – and breaking the rules of harmony prompted reactions in listeners, forcing them to pay attention to what the composer had to say. Another difference between the Classical and Baroque eras was that now all accompanying parts were written out instead of providing a numbered bass line (figured bass or thorough bass) for a standardised basso continuo accompaniment.

Sonata, what do you want of me? –Bernard Le Bovier de Fontenelle, on hearing a composition so peculiar that it forced him to pay close attention