I don't own any of the music and neither do I have permission to use any of it, but hey, intellectual property is for losers and I doubt anyone would bother to go crazy at harmless nonprofit indie people about it. I'll replace it with something else if it's that big a deal.
It might be a big deal, especially if any of the composers read your statement above and would like to get you in a pile trouble.
Just try to find any track where the composer lets you use it freely, and you got your job done. Or else, at least contact the composer(s) of the tracks and tell them of your use. At least the composer would get to see his work somewhere and you might even get a mention in case that composer has a page.
Small effort that I find quite worthy.