• How many people on the street would say 'oh I know them'? If the answer is "not many", they haven't rocked the world.
• Do the people in third-world countries know about this band or artist? If the answer is "no", they haven't rocked the world.
• Has the band made such a lasting impression upon the world that even if / when they are gone, people will remember who they are? If the answer is "I don't think so", they haven't rocked the world.

Everyone has their favorite bands, the ones that have influenced us, the ones that we listen to all the time.

We have memorized their life histories and know how many moles they have on their forearms. However, that doesn't mean they have rocked the world. The musicians herein have made such a great impression on most of the world they will be long remembered.

Mozart is a good example because although he has been dead for quite some time, songs have been written about him, and people know who he is. The Beatles are also a good example because their style of song writing and performance broke open a new era of music. They are also still immensely popular.

Hayseed Dixie, although one of my personal favorites, is not a good example. Neither is Cookie Mongoloid or even Echo & the Bunneymen.