To discuss "The Classical Style," the witty, charming, exhilarating new opera by Steven Stucky for the music and Jeremy Denk for the libretto, based upon the eponymous 1971 musicology treatise by Charles Rosen (eulogized here by Jeremy Denk in 2012), presented in the Ojai North Festival by Cal Performances, let's take a detour through the musical piece it most resembles: Frank Sinatra's "One Note Samba." O'l Blue Eyes croons "this is a little samba built upon a single note, other notes are bound to follow but the root is still that note" while at the same time singing exactly one note, an F. He switches then to another repeated note, B flat: "Now this new note is the consequence of the one we've just been through," returns to F for "as I'm bound to be the unavoidable consequence of " and back to B flat for "you!"
This is a self-referential tune which explains to you in the lyrics what's going on in the musical line. F is the root, the tonic, and establishes a tonality. Bb comes in, as the "consequence" of F. In musical terms, Bb is the subdominant of F, a tonality which attracts F, where F wants to resolve. Bb therefore creates an ambiguity: "oh, but I thought I was stable in F, and now F is drawn to Bb." It uproots F, demotes F from being the key center to hanging up there, waiting to fall in the arms of Bb, which it does on the final "you." The musical gestures mimics falling in love.