The usual metaphor for perfume notes and accords is music. The notes are like musical notes, and the accords are like chords, with a discrete sound. But a discerning ear can hear the individual notes within a chord. The same isn’t always true with scent.
Some accords create a scent that’s startlingly different from its component parts. Perfumers recall moments in formulation in which the accord turns on a single drop, becoming something utterly new and separate from its individual materials.
In this way perfume accords can behave more like light and additive color. For example, when red and green light are projected over each other, the result is an unexpected bright yellow.
Some well known accords are composed of individual notes that would surprise many. For example, amber accords contains no mineral amber, a fossilized tree sap which has very little smell. Nor do amber accords contain actual ambergris, whose scent they were originally designed to evoke. But amber deserves its own entry….