TWENTY-FOUR girls in identical royal blue pinafores, a lot of torn-up coloured paper, and one sculptor, slightly harassed, but hiding it well: this is an early stage in the progress of an intriguing project at St George’s School for Girls in Edinburgh.

r-indent = The idea, born of art teacher Sarah Knox, music teacher Sue Masson and an earlier project with the Scottish Chamber Orchestra, is to combine visual art and music in a joint process, ending with a performance or “happening’’. So every Wednesday for a month, the Primary 6 classes at St George’s are breaking out of their normal routine, to the chagrin of the games mistress (“That’s no more hockey this term, then.”), and exploring the theme of evolution through sounds and pictures.

The world evolves as you climb the stairs of the primary building. On the walls, wonderful explosions of shape and colour are labelled First Life Forms, Soup of Chemicals, Big Bang. Using a restricted palette, the pupils have been exploring the effects of colour and shape: the clashes, the rhythms, the control of cut shapes, the freedom of torn ones.

In the classroom, the sculptor, Jeremy Cunningham, towers over the swarm of blue pinnies, attempting to generate a great wave of creative enthusiasm and then bottle it within a 30-minute period. The girls are having a whale of a time creating a seascape on a grand scale, crawling over a vast piece of card laid out on desks and sticking on shapes to suggest the current, the spray, the eddies and pulses that give life to the sea.

“Think about how the different areas interact,’’ says Cunningham. “What happens when this torn, surging, dark night-time current meets this splashing daytime one? It’s much gentler. You can almost hear it going tinkle, tinkle. You two groups will have to talk about what happens in this unknown gap.’’ He pounces on a spreading seabed shape someone has cut out. “This is really exciting. It doesn’t look exactly like anything, but there’s an insight, a real feel of something.”

Cunningham has extensive experience of working with groups like this. “It’s not about having your own piece of work to take home and show mum,’’ he says. “It’s about feeling freer to take someone else’s work and develop it. If you are going to arrive at an interesting artwork, it’s hit and miss without that development process. It’s like being a fisherman. Experience tells you where you are likely to catch something. But you can’t be sure until you’ve caught it.”

Across the playground in the steeply-tiered auditorium of the music department, it would be a brave fish that stayed around to hear composer Stephen Davismoon at work with skins, wood, metal and tuned percussion instruments - and another 24 girls. A kind of co-operative composing is going on, inspired by the air, particles, space.

Davismoon produces a “time line’’, a basic rhythmical structure, and the group works out a scale of selected notes. Then off they go, producing a wonderful gamelan-like cacophony. Rainsticks rattle, maracas slap and tickle, drums pound, xylophones tinkle up and down.

Sue Masson is delighted with the project. “In this group we have two viola players, a violinist, a cellist, but this makes music-making accessible to everyone.’’ One “non-musical’’ child has been thrilled with the different sounds she can make on the xylophone by using the different ends of the beaters. It is the sort of discovery a “properly-trained’’ musician might never make.

Ultimately, the musicians will be “playing’’ the seascapes, earth movements and planetary big bangs being produced in the art workshops, using the shapes and colours as a kind of musical score. The sounds they produce will then be reinterpreted in the media of picture, words, movement and who knows what else.

The vocabularies of music and painting are getting mixed up in this project: the music teacher enthuses about sparks and swirls of sound; the painters talk about whooshes and bangs of colour. The barriers between disciplines are not so much breaking down as crossing over, making something new.