The fragrance of an essential oil can be characterized as being either a top note, a middle note, or a base note, just like the notes of a piano. The fragrance of a base note will last longer than a middle or top note.  The fragrance of a middle note will last longer than a top note.

          When using essential oils for therapeutic purposes, an essential oil having a base note will usually be used for deep tissue work, while an essential oil with a top note will usually be used for a psychological problem.