The symphony of smells-the name of this book is secret?

the symphony of smells was something Pietro and his brother invented which matched certain smells to letters and numbers. Because both brothers had Synesthesia, which the senses are sort of mixed up with each other, they could smell something and associate it with a letter or color. This was their secret way of communicating with each other. It is the item which introduced Cass and Max-Ernest into the terces society.