Did Led Zeppelin write the greatest song opening in rock history—or steal it?

For live audiences, Stairway’s power starts with its introductory notes. “Can you think of another song, any song, for which, when its first chord is played, an entire audience of 20,000 rise spontaneously to their feet, not just to cheer or clap hands, but in acknowledgment of an event that is crucial for all of them?” Observer critic Tony Palmer wrote in a 1975 profile. Dave Lewis writes in Led Zeppelin: The Complete Guide to Their Music that “Stairway has a pastoral opening cadence that is classical in feel and which has ensured its immortality.”

But what if those opening notes weren’t actually written by Jimmy Page or any member of Led Zeppelin? What if the foundation of the band’s immortality had been lifted from another song by a relatively forgotten California band?