ON BBC Four this past week, Danny Baker was convening panels of talking heads to discuss the state of pop and rock music over three decades - the 1970s, the 1980s, and the 1990s.

I caught only the first of these, and was glad to have done so, not least because the other contributors - Viv Albertine of The Slits, Peter Hook of Joy Division and New Order, and, somewhat surprisingly, Lloyd Grossman - were thoughtful and entertaining. The assertions that sometimes failed to stack up were those of Baker himself, in chairman and provocateur role.

On Monday he tried to justify the premise of his series by arguing that the division of musical evolution into neat decades was justifiable on the historical evidence. Methinks he protesteth too much for credibility. In fact, the first programme's most meaningful exchanges, backed up by sonic evidence, were designed to bury the canard that punk rock swept away an era of worthless indulgence and excess half way through the decade, so it would have been perfectly permissible to acknowledge the convenience of decades of definition while simultaneously undermining the idea that "1970s" or, more often, "1980s" music makes any sort of sense.

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It is, of course, the media that is entirely to blame, and specifically those in the media who do not really think very deeply about music at all. The publication in recent years of some fine social history of Britain's post-war years has successfully debunked many notions about the neat impact of the 1960s as the crucial decade of change, with the years on either side having just as strong a claim. What the second half of the 20th Century shows, in music as in much else, is a steady growth in the breadth of the interests of the people, so that finding one object or genre that encapsulates a moment in time becomes progressively more difficult.

The solution to this, in arts promotion, has been the rise of the well-defined niche event. The East Neuk Festival has become the template for popular chamber music events that use attractive venues to present top artists in an intimate setting. That festival's own literature strand, Littoral, is successful because it is thematic, majoring on nature writing, rather than just another of the boom in local book festivals.

You would be hard pushed to encapsulate Alasdair Campbell's Counterflows event, over three days in small Glasgow venues at the start of April, quite so neatly. This year it embraces local artists Ela Orleans and Luke Fowler alongside a residency by improvising saxophonist Joe McPhee and a performance in an underground car park in Garnethill by Japan's Akio Suzuki.

A month before that, the Arches launches the latest edition of its Behaviour season, a perfectly-named programme of performance that has become the brand for an audience looking for the sort of challenging new theatre work that will often go on to international success.

In that niche, the word "durational" is used to explain work that takes time to weave it magic. In the 21st Century we have learned it is the art that defines the time span, not an arbitrary time span that ever defines the art.