Given the lack—perhaps permanent—of good hard data, most of what gets written about Robert Johnson runs along the same rutted paths: a few facts, a few conjectures, a threadbare reminiscence from one of the usual grizzled informants, and that’s about it—pretty thin gruel, especially considering the richness of Johnson’s music. It seemed wise to me, when I set out recently to write about Robert Johnson for Musician magazine—for the third or so time—to seek less traveled ground: Johnson’s impact on some of today’s most influential pop musicians.

Rock ’n’ rollers aren’t scholars, and the nine I interviewed for the article (Andrew Franklin handled Keith Richards and Eric Clapton) often knew less about Johnson’s life and music than I did. But I found exceptions: the Memphis record producer Jim Dickinson, the great guitarist Ry Cooder, the blues singer John Hammond, Jr. (son of the famous talent scout). And factual knowledge isn’t relevant here. What matters is inspiration , the force with which these dozen imaginations have been gripped by one man’s music. It would be a mistake to equate Johnson’s influence with that of, say, the Beatles or Elvis. The latter are tidal waves, rerouting pop music in single, overwhelming instants; Robert Johnson is an underground stream. But when the roots nourished belong to Eric Clapton, the most admired rock guitarist of the last quarter-century, or to Keith Richards, the musical heart of the hugely influential Rolling Stones, or even to Robert Plant, whose Led Zeppelin sold tens of millions of albums to two decades of teen-agers, then the vast outline of Johnson’s shadow begins—with grandeur, bit by bit—to emerge.

Every one of our famous interlocutors was eager to talk, sometimes for hours, often with an acuity you just don’t expect from rock stars. As I wrote in Musician , “Ask them about themselves and they’re testy, glib or unreachable; ask them about Robert Johnson and you’ve got an interview.”

“He’s the one that laid it down for us all to pick up,” said Eric Clapton, interviewed last year in Manhattan. “And what’s amazing to me is that 50 years later, young musicians are still playing what he laid down without [their] even knowing it. They think I invented it, or that I got it from Jimmy Reed or B. B. King or Howlin’ Wolf, when in actual fact there’s one guy in the back of it all.”

Keith Richards, whose scruffiness and three-chord fundamentalism long ago elevated him into the paragon of the rock ’n’ roller, says, “You can hear Robert Johnson every time Eric Clapton plays, and hopefully now and again when I play too. He condensed it all, just like that. Everything you want to know about the blues is in those 29 tracks … and if you haven’t heard about him, do yourself a favor and give him a listen.”

He condensed it all…” That’s one clue to Johnson’s grip on musicians; he was a