How do you find out the soundtrack of a random video?

I don’t mean how to extract the audio from it, I know of some sites that provide that service (though only from youtube).
It occurs that I find videos throughout the net with a music put to it that I don’t recognise and would like to know the artist / composer.
Is there any way you know.
Of course I could post the video on a bolg by linking it and ask the users.. but that wouldn’t give a certain outcome.