I love analogies to music when it comes to describing some of life’s other pleasures. This happens to come from Whiff! The Revolution of Scent Communication in the Information Age and doesn’t mention beer, but you’ll get the point:
As any wine connoisseur can attest, aromas are often described in melodic terms as three distinct notes. In making perfume, top notes, middle notes and base notes are orchestrated like a symphony to tell a specific story in three movements. Top notes are the ingredients that create the first impression of the fragrance on the nose. They are the lightest and briefest of the fragrance on the nose. They are the lightest and briefest in duration, like high notes on a musical scale. In a well-designed fragrance, as top notes evaporate they harmoniously segue into the middle notes that comprise the main body, or second movement, of the fragrance. The middle notes evaporate at an even slower rate than the top notes, and also soften the usually stronger base notes. As the middle notes dissipate, the base notes linger like the finals strains of a cello concerto.
(Additionally, in The Secret of Scent, Luca Turin explains why odor molecules — and thus aroma — arrive in waves, repeating that the lightest are the first to arrive, heavier ones later.)
Before you stick your nose deep in your next beer and decide I’m an idiot, please note I’m not saying this works for every beer. Then the special ones wouldn’t be special, would they? As a general rule, beers you’d file under “less is more” seem to be the best candidates.