THERE must be some clause in the Scottish music documentary-maker's handbook that insists on a ferryboat shoot. After the cruise down the Clyde in Paul Fegan's Where You're Meant To Be, there are scenes aboard a cross-Channel vessel in Niall McCann's Lost in France, which had a cross-country link-up to screens across the UK from its Glasgow Film Festival event at the O2ABC in Sauchiehall Street on Tuesday evening. The two films share more than that, however, with a journey – and specifically musicians on the road – at the heart of the narrative, and a similar visual aesthetic and editing style.

But there is also a world of difference between them. While Fegan's film becomes an upbeat celebration of the musical tradition embodied by singer Sheila Stewart, who died before it was completed, McCann's remembrance of Glasgow's Chemikal Underground label showcase jaunt to Mauron in Brittany is ineffably sad. McCann's ostensibly daft notion of re-uniting the people who had taken Glasgow's music scene to a small rural French town twenty years ago is almost unbearably elegaic, with Stewart Henderson, the member of The Delgados who was the main driving force behind the label and who went on to create the Scottish Album of the Year award, the most clear-sighted – and, ultimately, bleakest – voice in the narrative. It is not as if members of the cast of the film have not gone on to bright careers. Henderson's bandmate Emma Pollock is a successful solo artist and her husband, the band's drummer Paul Savage one of Scotland's most respected recording producers. Stuart Braithwaite of Mogwai may have much less hair, but his band now plays the SSE Hydro and soundtracks art-house movies and TV series. Alex Kapranos – who appeared onstage on Tuesday with rather more hair than in the film – became the frontman of chart-toppers Franz Ferdinand. But the bigger picture is that other members of the group that created the label that went on the tour that the film documents are now moving to employment outside of the music business, and the bands that Chemikal Underground has championed in more recent years – whose music also features in the film – have had nothing like the level of commercial success of the Glasgow bands whose music they released in those days. For today's generation of twenty-somethings, the world of McCann's film is not the remotest possibility: rock'n'roll might still show plenty evidence of creativity, but it offers the prospect of a career to very few.

By happenstance, BBC Radio 6Music chose Tuesday to reveal further illustration of that. The 6Music Festival, which will fill venues across Glasgow in a month's time has as its headliners Depeche Mode, Goldfrapp and Jesus and Mary Chain, whose ground-breaking years are now decades in the past. There are younger, fresher talents to be found on the bill over the festival weekend, but the balance is not healthy and the idea that – to parallel Lost in France – a posse of cutting edge French musicians might turn up in the Dear Green Place and play to an appreciative audience is plainly ludicrous. But then a huge part of the success of 6Music is predicated on rock'n'roll heritage, and the danger is that, 'ere long, heritage rock'n'roll will be all that there is.