how can i rephrase this so that both parts are parallel Lots of my friends think that Prince's music is old, but I think it's not only excellent but also an innovation.
2 answers
You have two adjectives modifying "Prince's music" -- old and excellent. But that third one ("innovation") needs to be an adjective, too, not a noun.
Lots of my friends think that Prince's music is old, but I not only think it is excellent, it is also an innovation.