Nearly every thing google can find here some Search sting that help , just random (1) or specially artist (2) same small variations in order brings different results . Finally all what you do her is searching for a directory with Mp3 listed or in the header. Learn how to use the Google and experiment .
-inurl:htm -inurl:html intitle:”index of” “Last modified” mp3
2.Some special song or Artist
-inurl:htm -inurl:html intitle:”index of” mp3 “beethoven”
intitle:index.of + mp3 + “beethoven” -html -htm -txt
“index of” + intitle:mp3 + beethoven