Because a perfume is perceived as developing in layers, fragrance descriptions are often accompanied by a pyramid-shaped diagram of notes. A fragrance description is an attempt to translate the abstract nature of an olfactive perception into words that can help the reader form an idea of what the perfume smells like. Usually, the fresh and volatile notes are listed in the top of the pyramid, while the more long-lasting notes are placed at the bottom. In reality, though, this is only a theoretical picture, as many long-lasting notes are perceived at the very beginning of a perfume. Guerlain's scent diagrams reflect this fact, as illustrated above with Shalimar. The scent of vanilla is so powerful in Shalimar that it's the first thing we sense, and therefore vanilla is listed as a top note, as well as a base note.

Sometimes, the task of verbalizing a scent is straightforward, as in the case of lemon, because everyone is supposed to be familiar with the scent of lemon. More often than not, though, there are no direct links between the notes listed and the actual ingredients of the composition. One reason for this is that many perfume notes are better described with a common word than with the ingredient behind the note. An example of this would be the note of leather, which stems from birch tar. Only a few people know what birch tar smells like, but as this material traditionally was used for tanning leather, we readily associate the scent of birch tar with leather. Another reason is that many perfume notes are derived from synthetics. For instance, the scent of vanilla in Shalimar doesn't come from vanilla pods, but from ethylvanillin, yet the word "vanilla" is obviously more evocative than "ethylvanillin". In addition, most perfume ingredients have several different olfactive facets, like coumarin, which can be described as "tonka bean", "almond", "marzipan", "hay", "tobacco", and even "vanilla". Finally, perfume notes are often the product of several different ingredients occurring together. This is what perfumers call a "base". Think of the note known as amber. It refers to a blend of various balsamic and earthy-sweet ingredients, and is only called amber because of its golden colour. Other typical perfume notes that are a result of a base are lily of the valley, lily, lilac, hyacinth, and hawthorn.
(September 2015)

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