LIS RHODES' 'LIGHT MUSIC'

Tate Modern, to 28th October

I like the idea of installation art. In fact I tend to like it a good deal more than the reality. In the idea, you immerse yourself in an entire environment. Rather than standing before a framed picture hoping it has some effect upon you, you're already there – inside the flows of the artist's imagination, like some 'Fantastic Voyage' trip.

But all too often the reality feels gimmicky and unfocused, a grab-bag of pieces which don't really fit together or show any signs of having been thought through. It's like a collection of phrases masquerading as a novel.

Take for example 'The Tanks', the programme of “art in action” in the new wing of the Tate Modern. Things can be inventively eye-catching in the way that adverts can. You can wander through them quite happily. Just don't stand and look or, whatever you do, stop to consider any of this. That would be like paying attention to the little man behind the curtain.

What the works are most like is the space they're in - just not as good. For this new wing, with it's industrial-megalith look, is both assault on and tonic for the senses. It's the standard thing with contemporary galleries. The building is more stimulating than the works it's supposed to house.

Then, just when I was writing the whole thing off as a non-event, I tried out the final room. The room that feels such an after-thought you even have to walk through another piece to get to it. And encountered Lis Rhodes' 'Light Music'.

Where everything else was a non-sum of its parts, this was elegant in it's simplicity. Two light projectors at the ends of the room point at screens behind each other. The black-and-white abstract images they project actually become the score, read by the projector as a kind of notation which produces electronic sounds. You see exactly what you hear. And you see everything - unlike the projection box at the cinema, the projectors sit in open sight. Even the beams of light, which we normally think of as a kind of pipe, tramsitting information which only gets decoded once it hits the screen, become objects in themselves. The images are often so simple you can see them replicated in light.

As the projectors simply sit on the floor, it's pretty much impossible to check out the work without crossing the projected beam. Though the other pieces in the Tanks used projections, whenever someone wandered in front of one it felt intrusive – like someone jumping up in the cinema. Here it felt very much part of the process. I stood and watched the new arrivals. Some hugged the edges, only tentatively stepping forward. Others plunged straight onto the dancefloor, interacting with the projections. It worked like a kind of discotheque for modernists. Rhodes has commented she wanted to see “the audience engage with the film, rather than being outside of it.”

Remember the sales line for the game 'Othello' - “a minute to learn, a lifetime to master”? This piece works something like that. You can see each of the few elements straight away. But add them together, find an audience and the combinations then become limitless. The more you stay, the more you become aware of the changes and shifts, of the different effects different attendees bring with them. “The concept of cinema has always tended to straighten things out”, Rhodes has said. “'Light Music' does not meet this prescription. It is more or less different every time it is screened.”

In all honesty, I'd never even heard of Rhodes before. Apparantly she's been at it since the Sixties, with this piece dating from 1975 and is still up to stuff today. Here she is, describing her work and berating the lack of women composers...