This is the 3570th most frequent Spanish word.
interesar
"Interesar" means "to interest" or "to be of interest."
The verb 'interesar' is used with an indirect object pronoun to indicate what piques one's interest.
Me interesa aprender sobre historia.
I am interested in learning about history.
Here, 'interesarían' is in the conditional form to politely inquire about someone's potential interest.
¿Te interesarían las novelas románticas?
Would you be interested in romantic novels?
In this sentence, 'interesa' expresses lack of interest, with the subject ('la música clásica') being what fails to engage Juan.