Rock opera is a term that curries both favor and foreboding. There is, however, a difference between the concept album and the rock opera. Though the "rock" aspect establishes it as something outside the usual strictures of classic oratorio, a piece still has to have a narrative to be considered a rock opera. The best still hold up, which makes it no small challenge to identify the Big 4 of Rock Operas. Pennebaker's Ziggy Stardust and the Spiders From Mars and its companion soundtrack Ziggy Stardust: The Motion Picture, as well as Live Santa Monica '72.