Those familiar with music will know that the secondary theme of a Viennese Classical sonata exposition is presented in a contrasting key. Less well known is that this harmonic modulation is accompanied by a rhythmic and energetic intensification that both dramatizes and structures the music. From this perspective, sonata form emerges as the musical form of the Enlightenment. Felix Baumann shows how this approach yields innovative insights that are compatible with recent theoretical developments while also offering a fruitful complement to them. The result is a significant contribution to music theory, musicology, and music aesthetics, as well as an invitation to engage with the subject in new ways.