What do "fragrance notes" mean? Top notes like Lemon & Tea Tree are the most volatile & are the first to evaporate. Middle notes like Rose Otto & Lavender make up the heart of any blend. The base notes like Sandalwood & Ylang Ylang have an aroma that lasts the longest. Any kind of note can be therapeutic in the right blend. They are used more in relation to perfumes than they are to aromatherapy.