My vocation is more in composition really than anything else - building up harmonies using the guitar, orchestrating the guitar like an army, a guitar army.

There's too many good musicians around for the music around for the business to be sagging.

That's the music that I play at home all the time, Joni Mitchell. Court and Spark I love because I'd always hoped that she'd work with a band. But the main thing with Joni is that she's able to look at something that's happened to her, draw back and crystallize the whole situation, then write about it. She brings tears to my eyes, what more can I say? It's bloody eerie. I can relate so much to what she says. "Now old friends are acting strange/They shake their heads/They say I've changed."

We kept moving forward and didn't try to recreate the past .. the approach to each album was radically different every time. Many bands would have some success and, because they were locked into having a single - something we didn't have to worry about - they had to make sure there was something similar on the next album ... that was never the idea with Led Zeppelin .. the goal was to keep that spark of spontaneity at all times.

I remember one particular occasion when I hadn't played a solo for, quite literally, a couple of months. And I was asked to play a solo on a rock & roll thing. I played it and felt that what I'd done was absolute crap. I was so disgusted with myself that I made my mind up that I had to get out of it. It was messing me right up.

I think it's time to travel, start gathering some real right-in-there experiences with street musicians around the world.

When you hear the melodic structures of what classical musicians put together and you compare it to that of a rock & roll record, there's a hell of a long way rock & roll has to go.