That's when all hell broke loose.
"Be careful what you wish for," says Frampton now with a rueful smile.
Within a month of its January 1976 release, the album "Frampton Comes Alive!" was in the Top 10 and getting stronger as the weather warmed. He spent a record 17 weeks at the top of the charts, thanks to the singles "Show Me the Way," ''Baby, I Love Your Way" and the 14-minute "Do You Feel Like We Do," with its distinctive distorted vocal effect.
One day, his manager called and asked if he was sitting down.
"I said, 'Yeah.' He said, 'Well, you've just made history. It's the biggest-selling album of all time. You've just beaten Carole King's 'Tapestry' record,'" Frampton said.
"That's when I got nervous and a little bit anxious because to have the No. 1 album was unbelievable. I mean, I never, ever thought that I could approach that. But then to hear that, that's sort of surreal."
The English-born Frampton, now 65, is celebrating that crazy summer with a new release, "Acoustic Classics," a CD of stripped-down versions of his best-known songs that includes one new tune, "All Down to Me." He wanted his beloved songs to sound fresh and intimate, as if they were written the night before.
"I was very pleased that the songs held up," said the singer-guitarist. "Very early on, I learned that you can have a great band, you can have a great producer, great studio, everything can be right, but if you don't have great songs, you've got nothing."
After the monster success of the 1976 live album, the singer's big hair and good looks led his record company to repackage him as a pop star. His next album was rushed, against his objections, and didn't do as well. Nothing could.
"I've learned that a pop star's career is about 18 months but a musician's career lasts a lifetime. I kind of morphed — as quickly as I could — into a musician," he said. "It was a crazy period."
Gordon Kennedy, a Nashville, Tennessee-based songwriter and musician who has written songs for Eric Clapton, Garth Brooks and Ricky Skaggs, has worked with Frampton for 16 years. He calls him "above everything else, this ferocious musician."
"He is a guy who, in some ways, had to overcome his own image. And it wasn't an image that he necessarily created," said Kennedy. "All the while, he's just wanting to play guitar."
Over the years, Frampton acted a little — he had a part in "Almost Famous" and mocked himself in Geico ads — and worked with George Harrison and toured with old friend David Bowie, whom he had known since he was 12.
Bowie, who invited Frampton on his Glass Spider Tour, was a mentor. "For all of us, we've lost a genius, a one-of-a-kind. He taught so many people how to redirect your career — including me," Frampton said.
Redemption came in 2007 when Frampton's instrumental album "Fingerprints" won a Grammy Award, his first. "I was speechless at that time because it meant so much to me to get that vote of confidence as a player," he said.
"Over the last few years — since 'Fingerprints' — things kind of sped up. There's more demand for me out there live. I've been working really well every year. It's fantastic because I love to play live."
Frampton these days lives in Nashville, Tennessee, and is father to four kids, the youngest a college student at 19. He's come to terms with the album that defined his career.
"When I kick the bucket, the first sentence will be, 'known for the live album 'Frampton Comes Alive!' I know that," he said. He also knows how beloved his songs are, especially "Baby, I Love Your Way."
"I have actually met children conceived to that song," he said, laughing. "It was a very personal song to me and made me realize the more personal you make it, the more everybody else can see that in themselves."