There are so many dramas about music!
I think that based on your description, you might like Shut Up Flower Boy Band. It is a story about boys trying to get famous with their rock group. There is some romance but mainly it is about friendship (and has some really great music)
Then comes to my mind Tomorrows Cantabile (kr ver.)/Nodame Cantabile (jp. ver.) which is comedy drama about a dude who is trying to make it big in classical music. The main character is actually a girl but she is little crazy and follows him all the time. It is great fun but with more romance.
Maybe Dream High might also fit your criteria? I dont remember it much but i think one of main characters is very talented guy who has it hard to make it big. There is plenty of romance though...
I also rec Page Turner, which doesnt have male main character but it is about music and friendship. Its super short and very high quality.
Some other kdramas that are about music/aspiring artists but dont fit you criteria: Heartstrings, You're Beautiful, Monstar, The Liar and His Lover, Monstar, Hit The Top, Trot Lovers
