Madonna is in the Rock Hall of Fame so like you say it probably should be just popular music. But "rock" is so broad anyway I don't know where the lines are....probably somewhere right around Neil Diamond... whistle grin (just kidding all you Neil Diamond fans...)

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.