The Final Note is a music from the Plague of Shadows soundtrack. This is the dance theme of Mona and Plague Knight together, and an arrangement of Waltz for One using the tone of Tango of the Troupple King as a basis. It is Music Sheet #15 in Plague of Shadows. It can also be listened to in Sound Test after completing the campaign once.
Music Sheet #15 is unlocked by giving Percy 41 Scrap Sheets.
"Song of dancing! Oolong can't handle the romance!"