For Robert Plant, the song rarely remains the same. Half a century since his former group Led Zeppelin mapped out a pugnacious new standard for rock bands, the 69-year-old continues to evolve his sound. With current album Carry Fire earning some of the best reviews of his solo career, the twinkle-eyed Plant prefers keeping his “eye on the road” and sizing up his next musical project rather than wallowing in nostalgia.

Even so, when Plant reflects on the earliest days of his career, he sounds like a time-traveller baffled by the archaic age he was once inhabited. Prior to Led Zeppelin’s formation in August 1968, Plant had already released the three failed CBS singles – 1966’s “You’d Better Run” (with his West Midlands band Listen) and 1967’s “Our Song” and “Long Time Coming”.

“When I look at the advertisements that surrounded the [ads for the] very first records I was involved in – before Zeppelin even – there were cars where you had to buy the heater [separately], there were cars where you had to connect a parking light at night-time to your cigarette lighter or your battery!”

Now a shrewd international veteran rather than a golden-maned upstart from the countryside, Plant is bemused and philosophical about his enduring love of performance.

 “I used to look at [older] singers still singing when I was 17 and making my first record before Zep and think, ‘They shouldn’t be still doing that now! Who the hell is their audience?’. So if you’ve got a good audience, you’ve got a good life. If you can still play five-a-side soccer and your feet don’t touch the ground sometimes, just keep going. If only we had amnesia enough to not know how old we were, instead of the pendulum always being up high and ready to swing down and say ‘Oi! It’s over!’.”

While Carry Fire’s lead track “The May Queen”’s reference to ‘the dimming of my light’ evokes the mortality of Dylan Thomas’ famed poem “Do Not Go Gentle Into That Good Night”, Plant plays down the connection.

“The song is just about the end of that particular day and that particular episode,” Plant says. “My opportunities remain vast – and so are yours, by the way, this isn’t based on fame and fortune – so it’s about keeping your eyes open for all the collisions and the melding that can come.”

Some of the most interesting moments of ‘melding’ in Plant’s extensive music catalogue come from collaborations with female vocalists. From the vocal interplay with Fairport Convention’s Sandy Denny on Led Zeppelin IV’s “The Battle Of Evermore” in 1971 through to 2007’s Grammy Award-winning Raising Sand partnership with bluegrass star Alison Krauss, Plant is lavish with praise for his former collaborators. Does it feel like a dance when you’re engaging with a new vocal partner and learning how to move with one another?

“Absolutely, yeah – it’s a very good way of putting it, definitely. It’s intriguing and it’s really fresh. Both parties have to see what the measure is, what the climate of the whole thing is, whether it’s driven or whatever. With Sandy Denny that was my first attempt and it wasn’t a bad shot! I’d written the lyrics to “The Battle Of Evermore” and I just couldn’t sing them all. It was evident there was an A and B to every couplet, like a response to every verse, the response would be a warning or indication or advice. We didn’t sing harmonies, with Sandy we did those tail adds at the end, which were great.

“Working with Alison was great and she is a very fine, stated singer, then working with Patty Griffin, which was probably more electric as she has a totally different way of expressing the vocal and telling the story. Toni Halliday has a great voice – such an individual style, really good.”

Carry Fire’s recent single “Bluebirds Over The Mountain”, previously covered by The Beach Boys and Ritchie Valens, includes The Pretenders’ Chrissie Hynde as a guest vocalist. Plant is full of admiration for the former punk from Ohio.

“Chrissie, now she has so much chutzpah and alluring front to what she says. She doesn’t waste a syllable in her work – she’s like bam! It’s to the point and it’s very alluring and quite emotive what she has to say. The way she cracks her voice, it’s something special. “Bluebirds Over The Mountain” is a ditty, but it’s a great ditty. I sent Chrissie my version of the track and she said ‘Yep, it’s extreme psychedelia – I’m in!’.”

Now firmly entrenched back in the Black Country region of his birth after spending the earlier portion of the decade living in the US, Plant relishes the down-to-earth West Midlands community.

“Where I live, it’s very light and laissez-faire – there’s a great sense of humour here. I live not far from where I went to school. I’m not around all the time – I can’t be anywhere all the time – but I have really good mates here. I don’t hang out with the guys I play with too much, although we do have murder mystery weekends!”

Plant and his Sensational Space Shifters will soon return to Australia for Byron Bay Bluesfest, as well as solo dates across the country. Whether breaking sales records with Led Zeppelin in the ‘70s or pushing his artistry into exciting new realms as a solo artist, it’s been an astounding career so far. It’s a long way from his main vocation exactly 50 years ago: before Zeppelin took off, Plant was putting tarmac on Birmingham roads. Does the rock icon ever wonder if there’s a parallel universe where Robert Plant never followed his musical dreams and instead lived an anonymous life in a small Birmingham home with his family, spending his weekends at the bar or watching football with his labourer friends?

“Well part of that still goes on, but I don’t know how it would have been,” Plant says. “Before I was working on the blacktop, the tarmac, I was singing in folk clubs as well as being in bands, so I think I would have moved across to the post-bohemian thing that was prevalent in the early ‘60s folk world.

“You don’t have to worry about being in a big band,” Plant adds. “You just do the folk clubs and do what God gave you the gift to do.”

Carry Fire is out now through Warner. Robert Plant and The Sensational Space Shifters play Byron Bay Bluesfest on Fri March 30 as well as shows in Sydney, Perth, Melbourne and Adelaide. For more information, click here.