Fragrance Notes
Perfume is described with a musical metaphor as having three 'notes', which together produce the harmonious chord of the scent. The notes unfold over time, with the immediate impression of the top note leading to the deeper middle notes, and the bass notes gradually appearing as the final stage. These notes are carefully created with knowledge of the evaporation process of the perfume.
Top Notes
These are the scents that are perceived immediately on application of a perfume. Top notes form a person's initial impression of a perfume and thus, they are very important in the selling of a perfume. The scents of this note class are usually described as "fresh," "assertive" or "sharp." The compounds that contribute to top notes are strong in scent, very volatile, and evaporate quickly. Citrus and ginger scents are common top notes.
Middle Notes
The scent of a perfume that emerges after the top notes dissipate. The middle note compounds form the "heart" or main body of a perfume and act to mask the often unpleasant initial impression of base notes, which become more pleasant with time. Not surprisingly, the scent of middle note compounds is usually more mellow and "rounded." Scents from this note class appear anywhere from two minutes to one hour after the application of a perfume. Lavender and rose scents are typical middle notes.
Base Notes
The scent of a perfume that appears after the departure of the top notes. The base and middle notes together are the main theme of a perfume. Base notes bring depth and solidness to a perfume. Compounds of this class are often the fixatives used to hold and boost the strength of the lighter top and middle notes. The compounds of this class of scents are typically rich and "deep" and are usually not perceived until 30 minutes after the application of the perfume or during the period of perfume dry-down. Musk, vetiver and scents of plant resins are commonly used as base notes.