This should be in "Anime suggestions".
Anyway, here are some shows I can think of. Mostly solo violins:
Sora no Otoshimono - ep 10 has a whole orchestra
Ef - Tale of melodies - Kuze plays a violin
Ookami Kakushi - there's a girl playing violin
Mahou Shoujo Madoka Magika - There's this character that plays in the final episode on a violin in front of small audience on a big stage.
K-ON - a lot of instruments > mostly rock music.
Kumo no Mukō, Yakusoku no Basho - Two of the main characters played on a violin there.