Robert Plant can’t fathom the concept of retirement.

The former Led Zeppelin frontman, 73, says he is often asked about when he’ll retire but insists he has no plans to end his career. “People used to say to me, ‘Well, you must have done enough now?'” he told The Telegraph in a new interview. “Enough of f–king what? ‘Enough to retire!’ So imagine the blessing to be 40 years further down the road, and I still don’t know enough to stop in any respect. There’s always something new to learn, somewhere new to take it. I love it.”

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The singer adds that being a musician is a “lifetime’s job,” one that continues to provide him fulfillment and joy five decades on from his first foray into rock and roll. Plant, who’s released more solo albums than any other past member of Led Zeppelin, has been collaborating with bluegrass singer Alison Krauss since 2007. The pair just released their second album, Raise the Roof, a follow up to their 2007 Grammy Award-winning Raising Sand.

Since collaborating with Krauss, Plant has taken on a singing style that differs greatly from the powerhouse vocals he’s often known for. “It creates quite a feeling to hear him in that harmony role because the identity of his lead singing is so powerful,” Krauss says. “It’s a voice that’s been part of everyone’s musical experience for decades.”

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“It’s like being at night school,” Plant explains of working with Krauss. “I’m still learning the different flexing of harmonic options. You can hear me fitting in almost like some sort of vocal jigsaw puzzle.”

“Two generations from when I first started being addicted to this, I’ve still got a foot on the pedal,” he said. “I’m still going somewhere. It’s the prerogative of a madman!”