Listen to Sweet and Ritchie Blackmore join forces for a unique performance of Free's All Right Now

On March 24, 1976, glam icons Sweet played the last show on the US leg of their Give Us A Wink world tour at the 3000-capacity Civic Auditorium in Santa Monica, CA, less than six weeks after the release of the album that gave the tour its name.

The show took place just five days after the death of former Free guitarist Paul Kossoff , whose body had been found in the bathroom of a flight from Los Angeles to New York. Kossoff had been due to support Sweet in Santa Monica with his band Back Street Crawler, and the headliners took the opportunity to pay tribute.

For the encore, the band played Sweet F.A. before pausing to allow a very special guest to emerge from the wings: Rainbow guitarist Ritchie Blackmore , who'd completed work on the band's classic Rising album the previous month.

It was a special moment for Sweet guitarist Andy Scott, who'd been heavily influenced by Blackmore. Indeed, Sweet had performed Deep Purple classics Hush (originally by Joe South), Kentucky Woman (Neil Diamond) and Black Night in their early days playing dance halls, where patrons demanded to hear hits rather than unknown originals.

"It was completely spontaneous," Scott recalled. "We had met him a couple of nights earlier, and the one thing that he'd said to our tour manager, who used to work for Deep Purple a guy called Mick Angus was 'You'd better let me get into the gig tonight. Because the last time we'd played Los Angeles he hadn't been able to get into the show, because our management at that time and the record company had virtually sold out the gig even before tickets went on sale.

"Ritchie said to [Mick Angus], 'I'm gonna come, and I'm gonna get in this time.' And we said, 'Of course you are!' And somebody made the joke, 'If you want to get up, put your guitar in the boot.' There was an offer to set up another stack, but I think Ritchie just said, 'Plug me into anything, I'll be alright.'

"And I think the only amps on my side of the stage that were available for him to plug into were the amps that I think were monitoring the synthesisers, which had a couple of horns in them, which left him with a rather loud and clear sound."

The result was recorded, and while it has never officially been released, the Santa Monica show has been widely bootlegged. And, last week, Sweet uploaded the audio to their YouTube channel, giving the song an extremely belated seal of approval.