Ever since the first rocker took a Stanley knife to cinema cushions in 1955, popular music and film have been joined at the hip. No one in this British Film Institute study can account for why an old square as Bill Haley should fire the kids up into such an upholstery-slashing frenzy; maybe it's the great imponderable, not really the question a BFI text is there to answer.

There are a dozen or so essays in this book, attempting to explain and decode what no less an authority than Martin Scorsese in his preface calls "uncharted territory". Rock musicians scoring film, starring in films, films inspired by music and musical periods: most any combination of the above.

And for the most part this is good, solid stuff. Mark Kermode's introductory essay is a useful 8-page pocket guide for large pockets, and evidence that, on occasion, good scores have rescued crap movies. Editors Romney and Wootton provide complementarys on the ins and outs of the rock documentary. Kodwo Eshun contributes a helpful, lucid dissertation on Blaxploitation, from Sweet Sweetback's Baadasssss Song (1971) to Deep Cover and Juice, that benefits from concentrating on the music. And Ben Thompson's piece on that most difficult of areas - the acting rock star - neatly side-steps the most obvious of rock-stars-are-all-actors-anyway clichés. If for nothing else it deserves praise for highlighting the little-seen Slade in Flame (1974) as a key, unjustly neglected, rock film. (Mind you - it decides not to try and answer the question as to how the disgracefully untalented James Taylor and Dennis Wilson turned Monte Hellman's Two-Lane Blacktop (1971) into a compelling, nihilistic white-line masterpiece.) As Tom Waits opines: "Moving from music to films is like going from bootlegging to watch repair."

It doesn't all work. Jane Giles essay - As Above, So Below - attempts to probe the underground, transgressive cross-over, taking in the likes of Jarman, Jarmusch, Di Cillo (the marvellous Johnny Suede - Brad Pitt's finest screen moment), and Hillcoat (the relentless prison allegory Ghosts...of the Civil Dead). This is fine, but to have the so-called Cinema of Transgression as "taboo-breaking experimental cinema with cutting satirical humour" is pushing it a bit. The films of Nick Zedd and Richard Kern take childish delight in showing us their shit (more usually old porn loops, blow-jobs, cheap gore), and excuse it all by roping in Sonic Youth or Lydia Lunch or Jim Thirwell or Swans to credibly hammer away over the top. Neither big nor, indeed, clever.

And again, yet another almost-valuable reference text is circumvented by the lack of an index. A publisher like the BFI really should know better. (Though the extensive filmography is excellent.)

The final third is given to cut-up interviews with notables in the music-movie cross-over - among them Wim Wenders, Ry Cooder, Allison Anders and Michael Mann. Arranged under topic headings, they can throw-up the occasional gem (did you know, for example, that the irritatingly ubiquitous Tarantino considered ex-Velvet Underground supremo John Cale to score Reservoir Dogs?) but more often than not the style doesn't allow for the momentum to render them more than passably interesting. (And where is Alex Cox, surely the most musically aware of all directors?)

To be fair for a minute, the book was never designed to stand-alone, but as an informative, argumentative programme to a touring-BFI season of films and discussions. In that sense it achieves its goal - you keep wanting to toss the thing aside and dig out those old tapes of Quadrophenia or The Great Rock'n'Roll Swindle or Mean Streets or Stop Making Sense. And that can never be a bad thing.