"If the opening ceremony was the wedding, then we're the wedding reception," music director David Arnold told the Daily Telegraph.
Although organizers have tried to keep the ceremony under wraps, many details have leaked out in the British media and some performers have let the cat out of the bag themselves.
The Who, George Michael, Muse and Ed Sheeran have all said they will take part in a show that will include performances of 30 British hit singles from the past five decades whittled down by Gavin from a possible 1,000. The Pet Shop Boys, Annie Lennox and Fatboy Slim will also be on hand to get people dancing.
Gavin said Saturday the show would open with a tribute to the "cacophony" of London life, with a soundtrack ranging from the late Edward Elgar composer of the "Pomp and Circumstance" march to The Kinks' "Waterloo Sunset." Frontman Ray Davies is expected to perform the 1960s song, a love letter to London.
Thousands of athletes from 204 competing nations will march in and become a standing, milling audience Gavin dubbed them the "mosh pit" for the main section of the show, "A Symphony of British Music."
Details of the performers have emerged through tips and photos coming out of the rehearsal venue, an old car plant in east London. While creators of the opening ceremony could rehearse for weeks inside the stadium, Gavin and his team have less than a day between the end of track and field competition and Sunday's ceremony.
Gavin said he had 17 hours to get a show that involves multiple sets, pyrotechnics and 3,500 volunteer performers "from a car park to here."
The Spice Girls were photographed dancing atop black London taxis, so a rendition of their biggest hit, "Wannabe," seems likely.
So does an appearance by surviving members of Queen, whose "We Will Rock You" has been ever-present at the games.
Paul McCartney has already performed at the opening ceremony, but it's inconceivable that there won't be a bit of Beatles music in a tribute to the best of British pop.
And organizers will want to include younger acts such as Tinie Tempah, Jessie J, Emeli Sande and the Kaiser Chiefs.
Gavin would not say whether he had failed to secure any acts he had hoped to book though he said two who initially said no changed their mind after seeing the spectacular opening ceremony on July 27.
"There was no room," he said but would not let slip the names involved.
Gavin said the lineup was driven by the songs a hit parade of pop classics more than by the artists.
"It was more important the song made the set list, or the creative idea," Gavin said. "If the artist wasn't available, we asked someone else."
Like the Olympic opening ceremony, the closer will showcase British icons and British creativity. The Daily Mail newspaper published photographs of what it said was the ceremony's set, involving reconstructions of London landmarks such as St. Paul's Cathedral and Tower Bridge.
Organizers have said they want the ceremony to be a "cheeky" reflection of modern Britain, so expect touches of Monty Pythonesque humor perhaps even Python Eric Idle leading a mass rendition of "Always Look on the Bright Side of Life."
"It's not anything desperately profound," London games chief Sebastian Coe said Saturday. "It's not the opening ceremony but I think it will be great. It's basically a tribute to British music over the last few decades. It's fun."
There will also be an eight-minute section of song and dance created by the next Summer Games host country, Brazil. Expect samba, colorful costumes and some 300 performers, including supermodel Alessandra Ambrosio.
And of course there will be ceremonial elements, including the raising of the flags of Greece birthplace of the Olympics current host Britain and 2016 games host Brazil. Dignitaries' speeches "which hopefully will be nice and brief," Gavin said will be followed by the extinguishing of the Olympic cauldron, marking the handover of the games to Rio.
As with director Danny Boyle's opening ceremony, London is aiming for a plucky, irreverent tone far removed from Beijing's 2008 Olympic closer, which was heavy on precision fireworks, acrobatics and dancing.
Gavin said he was inspired by ceremonies like Sydney's in 2000, which showcased the vibrancy of Australian culture.
"They did 'Waltzing Matilda,'" he said. "They did stuff that said, 'Hey, we're Australian.' That's what our show does.
"Not that we're Australian," he added quickly.
Jill Lawless can be reached at http://Twitter.com/JillLawless