In 'pure' instrumental music, the strategies chosen by composers to create unity were responsive to the tenets of Romanticism...Even in the absence of an explicit program, motivic continuity created a kind of narrative coherence. Like the chief character in a novel, the 'fortunes' of the main motive – its development, variation, and encounters with other 'protagonists' – served as a source of constancy throughout the unfolding of the musical process.
Style and Music: Theory, History, and Ideology (1989)
"Because of the variables and the complexity of their interaction, the data assembled by descriptive musicology yield relatively few observable regularities."Leonard B. Meyer