This is a nice tip from Volker.
Googlebot runs across lots of directories with MP3 files. Here is how to find them:
intitle:"index of" -inurl:htm -inurl:html mp3
Of course you can add your favorite artist to that search string. If you put the full name in quotes you can make sure Google does not list directories that happen to list other artists that only share the first or the last name. Or you can replace mp3 with other extensions you are looking for.