Every song you played at Led Zeppelin's reunion show in London last year started with or was based on a killer riff. What makes a great Zeppelin riff?
It is something you know instinctively. It has energy and attitude. There's sex in it as well. It was definitely my concept to have a riff-based band. My influences were the riff-based blues coming from Chicago in the Fifties – Muddy Waters, Howlin' Wolf and Billy Boy Arnold records. "Boogie Chillen'," by John Lee Hooker – that is a riff. But you take it, absorb it and apply your own character, so it comes out another way.
Which happened that night. Your guitar-vocal interplay with Robert Plant, especially in "In My Time of Dying" and "Nobody's Fault But Mine," sounded brand-new, born on the spot.
In the Led Zeppelin shows of the Sixties and Seventies, it was the same numbers every night, but they were constantly in a state of flux. If I played something good, really substantial, I'd stick it in again. But Led Zeppelin were a working band in the truest sense. Even the rehearsals, in the run-up to that night in London, were dramatically different, in content and drama, from the show, which had its own character.
How hard was it to hear American blues and rock & roll records in Britain when you were growing up in the Fifties?
To hear current releases, you tuned in to AFN, the Armed Forces Network in Europe, and hoped that you could catch the title of something after they played it. We never got to see Elvis Presley until we saw his films. But the people who got sucked into rock & roll were collecting records, studying what was coming out of America. I had a friend who was not interested in a record unless it was by a black artist.
There was some blues in skiffle music. You got the songs, but the attitude and playing were not there yet. It was a learning experience, tracking these records down and finding the original sources – the Sleepy John Estes version of "Milk Cow Blues," Arthur "Big Boy" Crudup doing "That's All Right."
You just played along to the records?
That's what most of the British guitarists from that period did. You listened to the solo, lifted the tone arm and put it back down to hear it again. Once I was able to get a good guitar, my ability to work out what was being played on those records came in leaps and bounds.
How did your experiences as a studio guitarist in the Sixties – playing behind so many different singers – influence your writing and playing for Zeppelin?
I was very inspired by the [vocal] groups of the Fifties. I loved the way they worked, the perspective of the guitar within that sound. Blues was a pivotal thing on the first Zeppelin album. But I was playing acoustic guitar as well as electric in sessions, and I was into people like [American studio guitarist] James Burton. I wasn't into jazz so much – I preferred things raw.
For a short time, you and Jeff Beck both played lead guitar in the Yardbirds. Did you ever consider having a second guitarist in Led Zeppelin?
In the Yardbirds, when Jeff was there, we played the riffs in harmony. The approach was almost like a big band with brass – the power of that applied to guitars. In Led Zeppelin, I never considered having anything duplicated, because we were such a complete unit. We felt we could do anything in-house, certainly on the records. Once a song got on the road, those parts would change, especially where there were numerous guitar parts on the record. We used to do "Ten Years Gone" [on Physical Graffiti], and that's got lots of guitars. We did a pretty good version. It wasn't until I played it with the Black Crowes [in 1999] that I heard all of those parts live. That was a thrill.
How would you describe your tone – or the one you like most of all?
It varies. I've used pedals going all the way back, pre-Yardbirds. I was using a fuzzbox in sessions. But the engineers couldn't understand it. Anything radical, they couldn't deal with it. In the Yardbirds, I was trying the violin bow and the wah-wah, using distortion and echo. I had phase pedals and chorus pedals as time went on.
What attracted you to the bow? It is the signature sound in "Dazed and Confused."
It was proposed to me when I was doing studio work. One of the session violinists was the father of David McCallum, the actor in the TV show The Man From U.N.C.L.E. String players would keep to themselves, but this guy was quite friendly. He said to me one day – we'd just finished a session – "Have you ever tried bowing the guitar?" I said it wouldn't work. The strings aren't arched over the guitar, the way they are on a violin. He said, "Have a go." He gave me a bow. I tried it and realized there was something in it. I don't remember if I used it on any sessions, but I certainly used it the minute I was in the Yardbirds [notably on the 1967 single "Little Games"].
Your most famous solo is arguably the one at the end of "Stairway to Heaven." How much of it did you compose before you recorded it?
It wasn't structured at all [laughs]. I had a start. I knew where and how I was going to begin. And I just did it. There was an amplifier [in the studio] that I was trying out. It sounded good, so I thought, "OK, take a deep breath, and play." I did three takes and chose one of them. They were all different. The solo sounds constructed – and it is, sort of, but purely of the moment. For me, a solo is something where you just fly, but within the context of the song.
Young guitarists learn to play now by studying your riffs and solos. What is left for you to discover on the guitar?
There is a lot I can and should be doing. The main thing is quality. I've always had a high bench mark in everything I play. That won't change. The important thing is to commit to playing. You have to put a lot in to get a lot out.
The great thing about the guitar, when I was 12 years old, was that it was portable. It made the music accessible to me all the time. I could get together with my mates, and before you knew it you had the serious spirit of music there – even kids just playing a few chords. You can do it with computers and keypads now. But I'm interested in how you get that spirit on the guitar. Because that's my instrument of choice.
This story is from the June 12th, 2008 issue of Rolling Stone.