Picture the scene: it's late 1960s USA, campus riots are the fashion, anti-Vietnam War protests the catalyst.
In the maelstrom a band aligned with the growing urban counter-culture is sticking its head above the parapet, helping the masses bark defiance against their masters.
That band is Chicago Transit Authority, all radical stance and attitude. That band would shortly become . . . Chicago, kings of ballad rock, forever top of the slush parade thanks to the immortal, bullet and cynicism-proof hits If You Leave Me Now and Hard to Say I'm Sorry.
How did it happen that such a politically conscious outfit could blow its cool so spectacularly? Is it true that the band is now 30 years old? And where have they been since 1976? Chicago: the first 30 years was marked by the recent issuing of The Heart of Chicago, 1967-97 anniversary album, containing, yes, those two tunes, plus all the other old favourites guaranteed to drag a mist of reminiscence across the eyeballs.
And while they may have disappeared from view, Chicago never really went away, as bassist and vocalist Jason Scheff explained.
'We've been on the road with the Beach Boys recently, touring the States, and this autumn we have our own headlining tour of the States and Canada.
'This summer we're playing what we call 'the sheds' - the outdoor arenas - in front of 15,000 to 30,000 people; each year we spend about four months on the road, and every couple of years we get back to Japan. But it's been five years since we were last in Hong Kong. I loved it, although I seem to recall my wife buying some very expensive antiques.' Scheff, recruited in 1986 to replace Peter Cetera - composer of those hits - who ventured down a successful solo path, revealed the rationale behind the anniversary album.
Given that many of Chicago's better-known songs have been done to death on other compilations, didn't it look like a cash-in? 'The original band members finally recouped the enormous record-company advances paid to Chicago at the outset and bought back the master tapes,' said Scheff.
'In the meantime, various songs had appeared on different albums, but they thought it would be a worthwhile idea to put them out together for the big anniversary. And a couple of new songs appear, too.' There isn't much on the album to indicate a tougher Chicago than the one we all know and love. What happened to the musical fist-waving? 'Anybody who discovered Chicago's music in the '80s would have looked at us as forever a ballad group,' agreed Scheff.
'They would have no idea that we really do rock; we love to play hard and there is a big R&B influence on the band.
'But what happened in the early years was that the first album was a huge hit on college radio and the critics loved it.
'But then because Make Me Smile [a ballad] became a hit, critics accused the band of selling out and going commercial.
'Chicago were suddenly perceived as something they weren't.
'Because they struck huge the treadmill started. The music business 'suits' saw a feeding frenzy and wanted to do it again and again. Chicago, victims of their own success, were irreversibly a ballad band,' he added. Scheff admitted that 'power ballads' were now Chicago's indelible trademark.
'If You Leave Me Now and Hard to Say I'm Sorry are played live, of course. They were both number one hits and they probably get the biggest response.
'But we find that ballads have a worldwide appeal. Wherever we go we discover that people love those songs. They like to hear real melodies and that sort of stuff is timeless.' Scheff's big moment came when his decision to break out of the Los Angeles club scene, where he was playing cover versions nightly, and to push himself as a songwriter coincided with Chicago's search for a Cetera replacement. Chicago liked his style and the two were a match.
'I joined on the back of their biggest record deal ever; I walked into a very successful situation,' he admitted.
Scheff also missed the fallow years, in which Chicago were hit by the fall-out from punk and designated either fops or dinosaurs.
'There was a time when Chicago didn't even have a record deal,' he recalled. 'The band had been dropped by Columbia, although they were still touring. They never really went away.' Tragedy too left its mark on Chicago with the death of guitarist and original member Terry Kath in 1978. Kath, a firearms fanatic, inadvertently chose to play Russian roulette one night with a semi-automatic pistol - and lost.
But even that, and the hard times which followed, didn't deter Chicago's confirmed stayers.
They persisted in 'bringing everything to the party', observed Scheff, 'a few political songs, a few ballads, some R&B . . . they just put it all out there', and now, after the odd lineup change, their fortunes have turned full circle.
'A lot of people have grown up with this band,' said Scheff. 'Vietnam vets have told me how Chicago saved their sanity. A hit record can have a big effect on a large cross-section of people.
'If you see that you've changed people's lives with your music, that's a wonderful feeling.'