| Give this a shot...
1. Go to Google (www (dot) google (dot) com, just in case you weren't sure ^_^)
2. Do a search for [intitle:"index.of" (mp3) system.of.a.down -php -html -jsp -asp] (without the brackets [ ], but WITH those quote marks)
3. Replace "system.of.a.down" with the band name or song title you're looking for. Make sure to separate words with periods instead of spaces, otherwise it will search for any of the words instead of all of the words.
4. You can then bookmark this page, and if you're using firefox, try going into the bookmark's properties, change "system.of.a.down" to "%s" and change the keyword to "mp3".
5. Now, with step 4 done, you can type "mp3 any.search.terms" in the address bar and it will do the search for whatever you type after mp3.
I've just started using this, but it seems to work pretty well. You can also add other file types to search for by adding the file extension into the parentheses in the search terms, seperated by the vertacle pipe thingy (e.g. intitle:"index.of" (mp3|mp4|m4a|wma) system.of.a.down -php -html -jsp -asp). | 
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