A hard art to swallow

In a corner of the Liverpool Tate, two large video-projections are cast on to abutting walls. At first, both frames are blank. Then, slow motion, a male mouth, in profile and vast close-up, enters on the left and facing it, on the right, a female mouth enters. The male mouth begins to purse and wriggle.On the soundtrack we hear a heavily amplified articulation of mandibles. The female mouth, meanwhile, begins to stretch wide open, till it strains at maximum gape, and holds it, trembling yearningly. The naked mouth pouts - and suddenly gobs, and a comet of sputum flies across the frame, round the corner, into the other frame and disappears down the woman's throat with a loud plop. Then the walls go dark and the tapes rewind. This is Intercourse by Stephanie Smith and Edward Stewart. It's all over in a minute.

Intercourse is a juicy one-liner, but as these things go it's now at the trad end of the spectrum: a straight film for a viewer who stands before a double-screen. There are no buttons to push. The show doesn't change if you move about. Your involvement is just looking. But one day, and perhaps quite soon, when the virtual has got really real, and interactivity is total, just imagine: an image may be able to gob in your mouth, and you gob back in its.

"Video Positive 95" is the fourth biennial "UK Festival of Electronic Arts", and stress the subtitle because, over the years, the name has dated. Video itself is already looking primitive as an art medium. The days when a work might be a single tape playing on a single monitor and be found interesting are gone. I don't think there's one example in the various exhibitions showing around Liverpool over the next month. Complex installations and lively image manipulation are standard now. Interactive devices thrive. As yet, there are no virtual headsets and body bags. But these things will come.

In this field, the foreseeable future presses everywhere on the present, which makes it odd to say (and people do) that the electronic arts are still in their infancy - as if at some point in the future the whole business was going to grow up and settle down: so just bear with us. The situation, for both artist and audience, isn't like that at all.

The technology moves on inexorably, fast, with no plateau in sight, and it's not the artists who are making the going. Whatever is feasible asks to be used, but whatever is feasible (or affordable) now will shortly be superseded. The resistance of the medium will always be felt as a constricting limitation, not as a stable working resource. If it works perfectly, it's pass. The artist can't but think ahead to what could be done in the future but when that future arrives there'll be another one to think ahead to.

So the fact that a work's reach tends to exceed its grasp is more than a teething trouble, it's inherent. At the Bluecoat Gallery, for instance, you can see Marty St James's and Ann Wilson's Ark; a roomful of monitors, encased in ornate traditional frames, showing some of their "living portraits" - human heads, turning and changing expression slowly, but this time also melding and mutating into the heads of animals. It's intriguing and creepy, and it's done pretty fluently.

But we've seen that Michael Jackson video, we know that already (though at enormous expense) head-mutations can be done with quite astonishing fluency, a level of effect that Ark only nods to. And when such effects become easier and cheaper, will artists go back and perk up their earlier work? I'd guess not; there'll be some further not-quite-possibility on the horizon to aim for. Art will never catch up.

The progress of interactivity offers still more curious problems. These are partly practical. At the moment, the gallery experience consists too often in looking impatiently over the shoulder of someone who hasn't mastered the programme but won't let go of the mouse. There's something called The Toybox in the Tate, a CD-Rom with work by 20 artists within it - said to be very interesting, but I never got a clear shot at it. More than one terminal would be handy.

But even when you do get your hands on something, big hopes and small frustrations set in. As you find your way round the work, your sense of discovery and decision, at first so strong, begins to feel illusory. The choices turn out limited. You keep hitting the edge, coming back to where you've been, getting the same result, and start to wonder who is the real manipulator. Given a little freedom, you dream of much more, and of technology that would afford it - in short, start down this road and you want to become not just the seeker but the maker yourself. This medium, it seems, must subvert any idea of an artist-viewer relationship; not that it's got to this level yet, but every example holds out that promise.

Meanwhile, the artist can at least give you a good game. The best of these is Toshio Iwai's Resonance of 4 at the Open Eye Gallery, where you are making something yourself, and relating not just with the equipment but with other people. It's a music-making piece for four players: a rectangle of mouse-bearing podia, and projected on the floor in front of each one there's a chequer board with a cursor. You click on individual squares on your board. Each creates a note, and you find, as you play, that the x co-ordinate of the board controls pitch and the y co-ordinate time-intervals. The music circulates round, passing through each player's note sequence by turn, making them into a continuous rhythm/ tune, which can be complex (if the players are listening to each other) or chaotic (if they're not). You may go on adding notes ad lib, or clear your board and start again. It can go on for hours.

The interactivity in Judith Goddard's Tate installation, Reservoir, is more mysterious, as is the work itself. When your body breaks a beam it sets things off, but in these two dark chambers it's impossible to tell when you have passed through a beam, or if it was someone else. The components are resonantly elemental. A sudden electric spark produced by a Wimshurst Machine. A video projection of rushing water, hardly distinguishable from interference. Three tiny monitors dangling at eye level showing ECG graphs. Dripping water occasionally and disorientingly lit by a strobe. Even the catalogue-writer was rather impressively baffled.

The whole idea of interaction gets a rousing reductio ad absurdum in Ian Breakwell's and Ron Geesin's half-hour film, Auditorium, which had a one-off theatre-showing a week ago. We're watching, head on, the front rows of an audience, watching something to which only their reactions and the noises off give clues. They start off bored, move to attention and amusement, then to absolute hilarity and elation (is it circus clowns?), then to mild disgust and then (is an animal being slaughtered and cut up with a chainsaw before their eyes?) to face-hiding horror and outraged protest, then to delighted relief, then suddenly to abject terror (is the building collapsing?) - until at last you realise that they are watching nothing and that their responses, though carefully co-ordinated, are entirely self-generated. Catch Auditorium where you can, though I suppose the message really is: you don't need a show, you can do it yourself.