First things first: Don't buy her roses/chocolate/everything every single boy buys every year.
Romantic? Sure, for something that is stereotypical and requires no thought. It's almost insulting.
Buy her something she'll love. You say she likes music? I agree with what Martin said on the first page, and that was a nice touch with the gig tickets. Nice and personal. A love letters' a great idea. Anyone could send a loving e-mail/text, but a letter has that extra special touch, something tangible that she can keep.