This obviously comes from the new Google feautre, let's call is Google Music Search : you can get the same special result page as with the "more music results" link if you visit http://google.com/musicsearch and enter the same keyword there.

see: http://www.zorgloob.com/2005/12/google-music-search.asp

Thanks, I updated the post.

I can see links to buy tracks in iTunes Music Store..