It is the sort of dreich, wet Saturday morning when parents pull the duvet over their ears and tell the kids to watch telly for another half-hour. Yet outside St Mary’s Music School in Edinburgh’s West End, small, wet feet are trampling over sodden leaves and into the building.

In the whitewashed chapel of the former theological college, five- and six-year-olds shrug off coats and fling them on to a stack of chairs.

The atmosphere is what you would find in any primary classroom: girls huddle together and chat; boys fling themselves about the room, showing off their flashing-light trainers. Then the class starts.

The teacher has written something on the board. The class gathers round to see it. To most primary-age children it would be as impenetrable as ancient Greek. It is a series of letters boxed in by lines: s m r d ss mm r d.

“Who can sing this to me?” asks the teacher. Hands shoot up, and one of the boys manages a “beautiful, floating” descent from soh to me.

This is sol-fa, the system of teaching sight-singing which once had its place in every primary school, but which (pace Julie Andrews) has left most of today’s children untouched.

Here at St Mary’s sol-fa is alive and singing. Having mastered the little tune on the board, the class is gradually learning it by heart as the teacher, Frances McMillan, rubs out more and more until they are singing from an empty board. “You lot must have very special eyes,” she says.

There is a great deal packed into this 45-minute class, but the atmosphere of the Musical Workshop is light and relaxed; there is no musical hothousing going on here.

McMillan uses games, tricks and jokes to introduce the basics of musical performance and appreciation. After the singing exercise the children sort chime bars into order of pitch and take turns to play the tune they have now got firmly stuck in their heads.

Individuals come and try their hand in front of the class and are rewarded with enthusiastic applause.

Alexa, a seventh-year pupil at St Mary’s, has come to play the flute. “It’s my third instrument,” she explains to me apologetically, after giving a performance that requires no apology.

McMillan is quizzing the audience. “How does Alexa make a sound on the flute?” “She presses the buttons.”

“Oh, she just presses the buttons and the sound comes out?” “No-o-o.”

Questioned on their response to the music, the class is more hesitant. “Does anybody have anything they want to say after hearing that piece of music. ” Hands creep up. “My hamster died today.”

The class concludes with a boisterous musical game and a clever puppet show which introduces the ideas of volume, rhythm and musical notation, all in one neat little act.

The mums and dads come in, and before the first lot have got their coats back on, the next class is sitting down in front of the board.

In the parent-run cafe, coffee and biscuits are relieving that “too early on a Saturday” feeling. A straw poll reveals that, in bringing their children along to the classes, most parents are responding to the innate musicality that all young children seem to show, but that some are here because they feel there is not enough music taught in the normal school curriculum.

Their worries are apt in the week that the Associated Board of the Royal Schools of Music announced survey results showing that in only three years the proportion of children playing instruments has dropped from 45 to 41 per cent.

As always, it appears that only a certain sector of society has the wherewithal to make the difference for its own offspring. “It’s very much middle-class Edinburgh,” one mother mouths over her hot chocolate. “We’re about the only people who come here on the bus.”

Upstairs, the recorder ensemble is assembling. If you have never heard 14 recorders being played together in the confines of a small room, it is worth savouring the anticipation, but there is no doubting the skill and enthusiasm of both pupils and teacher. Again, the class is taken in an atmosphere of hardworking fun, but given that some of the players are as young as eight, it is striking how far they have moved on from their Musical Workshop days.

It is like a proper orchestral rehearsal: teacher Susan Fuchs expects the group to understand references to slurs, hemiolas, cadences and the difficulties of playing in 24 while being conducted in 34 time.

The recorder is an invaluable learning tool. Pupils start on the descant, but progress to treble, tenor or bass, thus gaining practical experience of the different fingering and keys of orchestral instruments.

While enjoying the experience of group music-making, the players are absorbing the discipline and etiquette of the orchestra, and learning a lot about technique by listening to each other’s successes and fluffs.

Harsh acoustics aside, the results are impressive. A spirited rendition of Shepherd’s Hey reveals all the texture of an orchestral woodwind section, and the Christmas concert performance of “Jingle Bells” will probably stop the traffic.

Outside the class, the parents of a brother-and-sister recorder team are waiting to get home for lunch. “It’s wonderful what they do in only 45 minutes a week,” says the mother. She is full of praise for St Mary’s, not least because both her children missed out on instrument teaching at their state primary, whose music teaching system she describes as “useless”. “This is the highlight of their week,” she insists. I look questioningly at the children, but there is nothing but glowing agreement in their eyes.

A SCHOOL IN TUNE WITH ITS PUPILS The Saturday classes at St Mary’s Music School began in the late 1970s after an advert was placed in the Edinburgh Evening News inviting parents to enrol their children in “musical play” classes. There were 20 replies, and the St Mary’s Saturday Morning Music School was born.

Twenty years later, the school vibrates with the music-making of more than 400 children every Saturday during term.

Jean Murray is the director of the Saturday School, a job she was cajoled into by her predecessor. “I wasn’t remotely interested to begin with,” she admits, “but it’s the best thing I’ve ever done.”

Murray also teaches at the main school and clearly appreciates the cross-over, encouraging St Mary’s pupils to act as assistants at the Saturday classes, a cross-fertilisation which is beneficial for all concerned.

The Saturday School began with the realisation that the wonderful facilities and expertise of St Mary’s were benefiting a relatively small number of pupils. The main school teaches around 60 pupils and entry is by audition, but the Saturday School is open to all. Fees are reasonable (currently from Pounds 1.65 to Pounds 5.90 per lesson) and the emphasis is on helping children to enjoy music and realise their musical potential. All teaching is in groups of various sizes, but the early years classes are so popular that there is a waiting list.

Classes for the younger children are designed to provide a musical background so that when they come to study an instrument all they need to learn is the technique. In the pre-school class the children play basic percussion, move to music, sing simple songs and listen to and discuss different moods of music, thereby absorbing the basic precepts of rhythm, pitch and musical expression.

“It is presented to the children as fun. They probably don’t think they’re learning anything, but if they’re enjoying themselves, they’re learning a lot,” says Murray.

There is a tendency for some children to drop out around P3. It may be because their own school is providing a lot of music, because they have chosen to learn an instrument privately or because other activities have taken over Saturday mornings.

It may also be because the changeover from general music-based fun to choosing and playing a particular instrument is a leap children, or parents, find difficult.

However, some children, says Murray, seem to soak up as much music teaching as they can get hold of: at school, in private lessons, and at St Mary’s.

The classes can be invaluable for older pupils. As all the teaching is in groups, it can be a great joy for a child used to solitary instrument lessons to find a roomful of kindred spirits and to discover the satisfaction of joint music-making.

Enquiries about St Mary’s Saturday School should be addressed to Jean Murray, St Mary’s Music School, 25 Grosvenor Crescent, Edinburgh EH12 5EL. Tel 0131-538 7766. Home tel 0131-226 3392