We all random sounds or random music from time to time. If you properly query google, you can find open indexes of music files easily. Here are some hints to get you started.

Google: -inurl:htm -inurl:html intitle:”index of” “Last modified” mp3

Using this string we are using the “index of” and the inurl commands to attempt to isolate directories only. The mp3 tag on the end tells google to look for mp3s in these open directories. You can change this to wma or ogg if you wish.
You can add additional search criteria to focus your search more.

Google: -inurl:htm -inurl:html intitle:”index of” mp3 “Orchestra”

This command will find open directories with mp3 files with Orchestra. Obviously you can change the name or file type to better define your search.