Four decades after Led Zeppelin released the rock anthem Stairway To Heaven, Robert Plant is still trying to decipher the lyrics.
The frontman of the top-selling British outfit admits that over the years he has become less comfortable with performing the eight minute-plus song.
"I struggle with some of the lyrics from particular periods of time and, I don't know, the musicality and the construction of it is peerless, but maybe I didn't quite feel the same about the lyrics later in life," Plant, 64, said of the song he co-wrote with fellow band member Jimmy Page.
"Maybe I'm still trying to work out what I was talking about."
The admission came on Friday as surviving Led Zeppelin members Plant, Page, 68, and John Paul Jones, 66, promoted the upcoming release of the film, Celebration Day, which showcases the band's 2007 reunion concert at London's 02 Arena.
More than 20 million people applied for tickets to attend the December 10 gig, with a worldwide lottery awarding admittance to a lucky 18,000.
The band insist that first and foremost the performance was a tribute to friend and Atlantic records founder Ahmet Ertegun, and that plans to produce a film were an afterthought.
"It was never definitely going to come out as a film. It was very important to the band ... that it was all about what was going to happen on the night," director Dick Carruthers said before a preview screening of Celebration Day in London.
There were no boom cameras permitted at the concert, with just a few dotted throughout the crowd. The film makes use of snippets of hand-held footage by audience members for cutaways.
However, Page admits that when it comes to audio, there was some polishing of the screen version.
"If I say there might have been a handful of fixings, in fact what I'm really saying is (it was) the minimum compared to what other people would do," he said.
"The concert was what it was - there was very little that needed to be messed about with because we'd really done it well in the first place."
With Jason Bonham - son of the band's late drummer John Bonham, who died in 1980 - sweating it out on the kit, the group perform 16 tracks as part of the two-hour show.
The catalogue included landmark numbers Whole Lotta Love, Rock And Roll and Stairway To Heaven.
"It's difficult ... choosing songs from 10 different albums," Page says in the film of selections for the 02 line-up.
"There are certain songs that have to be there and this is one of them," he adds, by way of introducing Dazed And Confused from the band's 1969 debut album.
Retaining his trademark frizzy long hair, Plant still managed to lift his mic stand, at one stage above his head, for the 2007 concert.
Lips curling with delight, silver-haired Page overcame a slight paunch and managed to end the winter concert drenched in sweat.
And it was a forever subdued Jones who switched between bass and keyboard.
Having enjoyed a reignited "chemistry" for the reunion, all three men admitted a sense of relief once their latest concert was over, and avoided answering questions about the possibility of a future performance.
* Celebration Day will be screened at select cinemas across Australia on October 17. Tickets are available at ledzeppelin.com. The CD and DVD will be available for purchase from November 16.