Greg Lake takes fans inside one of Emerson Lake and Palmer’s most spectacular 1970s-era concert stunts — when Keith Emerson would rise above the crowd playing a grand piano and turn 360 degrees.

Greg Lake confirms that Jimi Hendrix was considered for a spot in the earliest incarnation of Emerson Lake and Palmer — and that he was utterly aware of how that might have changed things when it came to the group’s name.

Even Emerson Lake and Palmer, whose name would seemingly ensure that they wouldn’t become another in the progressive rock genre’s endlessly interchangeable bands, endured a memorable roster shift. Greg Lake says he still regrets it.

Greg Lake offers something greater than mere retrospective here — though, certainly, there are familiar tunes from King Crimson and ELP. With its powerful sense of reminiscence, Songs of a Lifetime ultimately becomes a more personal journey.

Blame a meddling music label for Greg Lake’s fortuitous switch to the bass. He says childhood friend Robert Fripp needed a frontman for King Crimson — but Fripp, of course, already played guitar.

There’s a reason this April 6, 1974 concert, held during the sprawling California Jam at the Ontario Motor Speedway, has for so long been a favorite among bootleggers.

Greg Lake marvels at how current “21st Century Schizoid Man,” recorded during his co-founding stint with King Crimson in 1969, continues to sound some four decades later. So much so, in fact, that it was sampled by Kanye West.

After associations both with King Crimson and Emerson Lake and Palmer, it’s unlikely that Greg Lake will ever be identified as anything other than a prog-rock icon. Still, he’s trying to push out at the edges of that stereotype.

As Greg Lake continues his celebrated one-man “Songs of a Lifetime” tour through the UK and Italy, I returned to this 2-DVD career retrospective from Image Entertainment/Warner Music Vision.

In the heady days of the 1970s, prog-rock bands like Yes and Emerson Lake and Palmer were thought to be rivals, trying to top each other in every way — from elaborately constructed tours to even more elaborately constructed albums.