Arts: As seen on Radio 3

Trying to describe the visual arts on the radio sounds like a waste of airtime. Yet, argues Tom Lubbock, far from alienating listeners by denying them the whole picture, the attempt can give us all an insight into the dynamic quality of the act of drawing itself

On radio, so they say, you get the best pictures. They mean, of course, because you supply your own. It's a curious thing, the process by which a listener to a radio drama "sets" it in some specific place. You're often unconscious of having done so, until the point when the location in your mind's eye utterly refuses to fit some turn in the play's action. Then you find that the setting you've filled in is one you knew already, and perhaps had long forgotten.

Radio is very good at inciting visual memories, calling them up more vividly and in more detail than the memory might manage unassisted. But it is very bad at communicating new visual knowledge, at giving you images you don't already have in stock. For instance, it would be well nigh impossible to visualise, from radio news reports, however elaborate, even an approximate map of the former Yugoslavia. You need to see it. And what about a drawing?

Over five evenings last week, on Radio 3, there was a series of short programmes called The Outline Around the Shadow, presented by the artist, teacher and curator Deanna Petherbridge. The subject was drawing, and this is her big cause. Petherbridge is Professor of Drawing at the Royal College of Art and she organised the much-admired 1991 touring exhibition, The Primacy of Drawing. These programmes were admirable too - though for a reason that seems at first a serious obstacle.

Petherbridge began with the classical legend from which she took her title. A Corinthian maid traces the edge of her lover's profile cast by lamplight on a wall: the first drawing. Each 20-minute broadcast followed a theme - private and public drawings, the body, nature and the sketchbook. They mixed history and theory with studies of particular examples, drawings ancient and modern, famous and recondite, in chalk or ink or wash. The passion and precision of these descriptions was exemplary. Yet, if you didn't hear the programmes, you may be thinking: isn't there an obvious problem here?

To be sure, it must have occurred to Petherbridge and her producers that there might be something odd about art on radio. Perhaps it's not really odder than doing art in books or newspapers, nothing more than the old problem of words and images. But it certainly seems odder, especially the way Petherbridge does it. For several times in each of these programmes there are moments when she goes "live". The studio-talk acoustic changes audibly to a location acoustic; we are suddenly in the National Gallery or the Ashmolean Museum; and we hear Petherbridge say, "I'm now looking at..."

You don't doubt that she is. You hear her looking as she speaks, each phrase formed in front of the drawing itself, each pause becoming another glance. It gives a sense of immediate contact. Yet what is gained in immediacy is lost in inequality. Listeners can't but be conscious that they, by contrast, are not now looking at this drawing. And this removal is far more acute than with print, because print can seldom claim such direct simultaneity. The writer says: there is this picture which I have seen, and you might too. But the live radio broadcaster says: there is this picture which I can see at this moment, and you can't. And what can the listener do - imagine?

Petherbridge is looking, say, at Claude Lorrain's View of Monte Mario, in the British Museum, her voice hushed and close-up against a background of ambient gallery sounds: "A wash drawing, full of evening effects - there's not a line in sight - a view across a plain which has been interpreted simply in terms of blots of darker and lighter ink - there's a sense that he worked on a very wet piece of paper, where he moves into the wet to pick up the edges of the foliage, the roundness of the trees - a pulled- along line that indicates an edge of a lake or perhaps a road in a misty evening light - sometimes with a really loaded brush, you can see it dripping on to the page, and in other areas in a slightly drier way..."

Whatever is lost in my transcription, and lost in the reproduction on this page, I hope you can see the truth of this description. But, of course, you couldn't see that at the time of listening - and I hope it's clear also that, from the description alone, you'd have got very little idea of Claude's actual image. Imagine trying to sketch it out "blind". What would you have visualised? You've no idea where anything goes. Or, better still, try the exercise without any reproduction to helpfully interfere with the imagination.

Here is Petherbridge live in the Ashmolean, on Federico Zucchero's A Man Drawing by Moonlight: "It's a rather tall drawing and shows a very tall Roman doorway, with the shutters open, looking out on to a river, and in wash is the effect of moonlight on the river, a dark bridge and in front of this doorway is the little bending figure of an artist, bending over and trying to draw by moonlight - all of this is simply done in a brown wash and some very faint little pen outlines - an icon of the artist who, even though he can't see what he's doing, he's busy drawing at night..."

Now admit that, if you don't know Zucchero's work (and I don't myself), you're far more in the dark than the little bending artist. There's no cause to doubt the description's accuracy and it sounds pretty specific. You would surely pick the drawing out from an identity parade. But as to the image, you draw a blank. If you visualise anything, you do so knowing that it's the roughest, wildest guess. There's no room for visual imagination. There is a real picture, and if you saw it now, you could only expect to be surprised.

So, no visuals and no reliable visualisation. Yet something comes across, and something more, and more valuable, than the presenter's enthusiasm; rather more, even, than would come across from a similar programme on television. The series in fact offered a practical demonstration of drawing as a peculiarly radiophonic subject. Visualisation is not finally an obstacle, because drawings are not simply images.

Drawing is human action. Drawn representation is always at the same time the marks of a moving hand. Chalk, pen and brush, as Petherbridge stressed, don't cover their traces in the same way that paint usually does. Drawing declares its own activity on its surface. It shows its working. It happens live - and a live speaking voice can be its perfect interpreter. Go back to that description of the Claude landscape. It isn't so much a description of a picture, more a running commentary on its materialisation, on the motion of brush and wash over the paper, the drops, touches and dissolves.

Or, when the work is linear, like Leonardo's furious deluge drawings and Daumier's figures emerging from tangles of wiry lines, Petherbridge sets our attention on the flow, violence, and accumulation of strokes, their flicks and jabs and coils. What these programmes emphasised is how many of drawing's effects are kinaesthetic and sensuous: not just about dark/light, but about quick/slow, hard/soft, rough/smooth, wet/dry. What we call visual art, even when we look at it, involves sensations that are more than visual. And these sensations - unlike the images themselves - are far from lost on the listening imagination.

By contrast, television's urge to illustrate actually gets in the way. It's not only that TV hates stills, and takes desperate measures to try and animate them. It's the way the relation between scanning camera and static image makes the picture into a fait accompli, something that is already all there and all done, just waiting to be revealed. Radio is positively advantaged by its invisibility. It can realise the drawing process touch by touch, and because you can't see, you can't see what's coming up next. The live radio voice, which puts the looked-at image at such a remove, brings its action very close.

Now, of course, I must not suggest that drawings don't need looking at - they are organised images too, and the most vivid evocations are helplessly abstract - nor that Petherbridge didn't make you want to look at them: she did. But then invisibility had another benefit. There was no danger of the programmes being a substitute for the real thing. What The Outline Around the Shadow provided was an ideal preview (or whatever is the aural equivalent of a preview), and a lesson in how, when it comes to art-broadcasting, some things are better heard and not seen.