Analytic practice usually attempts to bridge the gaps between formal sections in a single movement or work by identifying thematic connections, syntactic logic, or structural cohesiveness. The gap itself is viewed as a foreground obstacle to be smoothed over by analytic insights. This article demonstrates that the moment of transition can play an active role in generating relationships among formal sections of a work. This is particularly apparent in a number of Haydn's symphonies, where the music at the end of a slow introduction seems to “generate” the opening of the fast section that follows. Haydn frequently—and most impressively in Symphonies 90, 91, and 92—forges a local melodic relationship between the adjacent edges of the two sections, with the moment of transition serving as an axis of symmetry. Furthermore, the “action” of the moment of transition on the music often recurs elsewhere in the movement, suggesting that such active transitions could be of interest in the analysis of other formal junctures as well.