Similar Music

I can't really find example, just some times I feel like I've heard music before from another anime, whether it be during a fight, or sad part, or even during that middle part of the episode, the eye catch parts.
Any one else notice similar music, not sound effects but actual music pieces like that.

Yes. I think Canon (Pachelbel) and Gymnopedies. I've heard Gymnopedies no.1 in every type of anime there is, and hentai too.

I don't know the piece of music but often I hear this same type of Violin music, only lasts like 10-30seconds at the longest, i've heard it in a few animes, any one else know what i am talking about?