You spray a perfume in the morning, and by the end of the day someone asks what you are wearing. You hesitate, because it is no longer quite what you smelled from the bottle. Most people conclude that the perfume has faded, or that their skin cannot hold it.
What we call a note
It is neither. What you smelled from the bottle and what you wear in the evening are two moments of the same composition, and the gap between them was decided in advance.
The word note comes from music, and it is slightly misleading. In music, the notes of a chord sound together. In perfumery, they leave one after another. A note is not an abstract smell: it is a raw material, bergamot, incense, vanilla, with its own behaviour over time.
A neighbouring word comes up often and is worth telling apart. In perfumery, an accord is several materials assembled to be perceived as one. You do not smell the six materials of a leather accord; you smell leather. The fragrance notes you read on a product page therefore rarely describe the exact contents of the bottle. They describe what the composition gives you to smell.
It all comes down to evaporation
The lighter a material, the faster it leaves the skin. The smallest molecules evaporate almost at once. The heaviest cling on and stay when everything else has gone.
That is the whole explanation. Citrus and aromatic materials are volatile: they reach you first and do not last. Flowers, spices and fruit hold on longer. Resins, woods, vanilla and musks are heavy. They leave slowly, and can still be read on a scarf long after you have stopped thinking about them.
No two materials evaporate at the same rate. A perfume therefore cannot smell the same from start to finish. This is not a manufacturing flaw; it is the starting condition.
Top, heart, base
The three terms describe nothing more than these three moments.
The top is what you smell the second you spray. Citrus, green notes, pepper, herbs. It is bright, and it leaves. It is an entrance, not a portrait.
The heart appears as the top withdraws. Flowers, spices, ripe fruit. This is where the composition settles, and it is most often what people have in mind when they say they love a perfume.
The base barely moves. Woods, resins, balms, vanilla, musks. It carries the rest, holds the heart back instead of letting it slip away, and it is what you find again on a coat collar.
The transition matters more than the list
These three tiers are often drawn as a pyramid, the top above, the base below. The image is convenient. It suggests that a perfume is a stack of three blocks, which it is not.
The three overlap constantly. The base is already at work while the top speaks, and what you call the heart of a perfume is almost always a heart mixed with what remains of the top and what rises from the base. The work of composition is as much about these transitions as about the choice of materials.
This is where compositions part ways. One whose top and base have nothing to do with each other feels like two perfumes glued end to end: you can smell the seam. A well-held composition moves without anyone being able to say when it changed.
What it changes when you wear one
Two practical consequences.
The first: judging a perfume by its top means judging it by its most fleeting part. What you smell on a blotter the instant you spray says almost nothing about what you will wear afterwards. A perfume is judged over time, not at the counter.
The second: your skin destroys nothing. It speeds up or slows down evaporation depending on its temperature and its nature, so the same perfume unfolds at different speeds on different people. That is why a perfume lasts a long time on someone else and far less on you. It does not become another perfume; it simply moves faster.
A perfume is not a smell; it is a length of time. You only know it once you have worn it for a whole day.
