Through his henchman, Fife the enchanted piccolo, he tried to destroy the Beast and Belle's relationship, promising him a solo in B Flat (though he never actually intends to give Fife the solo). He tried to persuade the Beast that love was meaningless and that his music was all that he just needed. When that failed, Forte tried to convince the Beast that Belle doesn't care about his true feelings for the holiday (though Belle doesn't actually know about them yet), which led to a serious argument between Belle and the Beast. This too also failed, as Lumiere convinces the Beast of a Christmas gift that Belle made for him as it shows how much she cares about him, which prompted the Beast to have another chance with the holiday. Seeing this, Forte makes another attempt by luring Belle with his music and convincing her to go down the treacherous Black Forest to find the perfect Christmas tree (despite Belle's promise never to leave the castle grounds), which Forte states to be the Beast's favorite part of the holiday, though it is not true.
As Belle fell into it, Forte informed the Beast that she has "abandoned" him, leaving the angry Beast to revert back to his hatred of Christmas and take Belle back to the castle before locking her up in the dungeon for breaking her word, much to Forte's sensational delight. However, the Beast finally regained his senses after opening up his Christmas gift, which turns out to be a book written by Belle, explaining the true meaning of Christmas. Through the words of the book, the Beast finally sees that Belle never intended to leave him and instead tried to bring back his Christmas spirit as promised, and that the greatest gift that anyone could receive was hope. Seeing that there could still be hope to break the spell, the Beast decides to release Belle, much to Forte's objections. The Beast then apologizes for his actions and allows Belle and the rest of the servants to celebrate the holidays, much to their delight.
Knowing that there will be a chance for the spell to be broken, Forte, refusing to "fade into the background", decides to bring the whole castle crashing down, intending to kill everyone inside, since no one can fall in love if they are dead. He creates a destructive earthquake that rattles the castle by playing a grand tune at sonic sound levels. Fife tried to stop him as the plan was too extreme, but Forte refused and revealed to him (via exposing blank music sheets) that his promise to give Fife a solo was a lie.
Upon seeing that the castle is in danger, Belle and the Beast break into Forte's room, where the Beast angrily berates his composer for his actions, demanding him to stop. Seeing no more in his heart to listen to the Beast, Forte refuses to stand down and instead continues rumbling the castle with his music, unleashing the full might of his power, and uses note shaped lightnings to strike his own master.
Avoiding the lightning, Fife advised the Beast that he must destroy the keyboard to stop the music. As such, the Beast decided that his own best friend was too dangerous and harmful to remain alive, and he ripped Forte's keyboard away from him and smashes it, which ceased his contact with his pipes. In a blind rage, Forte tore himself free of the wall and began to collapse. This effectively "kills" Forte and he slams down to the ground screaming in defeat, finally destroyed and silenced.
Though the Beast finally knew Forte's true colors, he ended up mourning the death of, what he considered, his best friend, with Belle comforting him. With Forte defeated, the whole castle continues to celebrate the holidays as planned, as Fife would later take up Forte's job as the new composer.