Is there a possibility that some song from previous games are in FO4?, I mean there is a radio channel that is named classical music.

or is it actual classical (violin,viola,cello etc...?)

I don't think that's likely, although Fallout: New Vegas used quite a few ambient tracks from previous games.

One of my favorite tracks from New Vegas is also a song from Fallout, "Metallic Monks". I kinda hope to hear something somewhat similar to that in Fallout 4, at least something with that same haunting feeling. The use of an air raid siren is featured in the trailer, after all, why not an ambient song? Metallic Monks II, perhaps?

As for licensed songs, that's also not likely. Maybe not entirely out of the question, I hear this soundtrack is considerably larger than Fallout 3, but I still doubt it.

Someone who played the game said that Diamond city plays songs from Fallout 3, and also new songs.