Open Google search engine and then put this string in search box:
‘ -inurl:htm -inurl:html intitle:"index of" "Last modified" mp3 ‘
Hit search button.
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.