The Symphony of Smells is a box with multiple vials that each carry a different scent. It was given to Pietro and Luciano Bergamo by Ms. Mauvais, and when he was in the circus with his brother they used it to communicate dates, numbers and such. Cass and Max-Ernest find the Symphony of Smells amid the piles of junk Gloria Fortune brings to Cass' grandpas' home. The Symphony of Smells is destroyed during the fire at the Midnight Sun.

It is said to be decorate in art nouveau style and to contain ninety nine vials arranged in four semicircles. It symbolizes the sense of smell.

The last remaining vial was given to Pietro in the fourth book "This Isn't What It Looks Like" by Dr. L, trying to prove that he has changed.

Some smells contained are:

  • Peanut Butter
  • Licorice
  • Sulfur (Rotten Eggs)
  • Root Beer
  • Lemon
  • Mint
  • Lime
  • Wet Wool
  • Old Socks
  • Freshly mown grass
  • Juniper
  • Chocolate
  • Allspice 
  • Rosemary
  • Lavender
  • Ginger
  • Maple
  • Vanilla
  • Heliotrope
  • Echinacea
  • Mandolin-Rose