Well first of all, if it's music you're after, you can specify that you only want to search for .mp3 files in the dropdown menu on the "Find" page.
This will not be totally "secure" though, as you have the likes of Wrapster, which is really .zip files for instance, but with the .mp3 extension. But you'll mostly get mp3's then.

About getting different results from what you searched for(like in your example), it sometimes is caused by the fact that the "porn guys" put a normal non-porn related name first, then a long gap, and then add umpteen porn words after.
Search for "UFO area 51 video", stretch the file-name bar so you can view the whole file name, and you'll see what I mean....

WHY they do this, I have no idea. Probably 'cause they think they're funny, and like messing with people.