Music is the last thing you expect to hear in a maths lesson, which is probably why it takes a while to sink in. That and the fact that the volume is turned down low, so low that you wonder at first if what you are hearing is music at all, or some documentary soundtrack wafting in from the next room.
But yes, there it is again, that short guitar run, just a three-note phrase that echoes and fades, and then returns in a slightly different form. And what's that in between? Birdsong? And could there be a babbling brook in there somewhere?
Double maths was never like this in my day. And it's not just maths. Drop into any lesson at Pensnett school of technology in Dudley and the chances are you will hear something similar. It's all part of an experiment to see whether music can aid learning and improve behaviour. And so far, the results are positive.
Not that this is just any old music. Ever since 1993, when Frances Rauscher and his team at the University of California told the world that listening to Mozart enhanced spatial intelligence, everyone from nursery nurses to turkey farmers has been playing classical music to their charges.
But Vo Fletcher, a professional guitarist with years of experience writing and performing activity songs for young children, has gone one step further by composing music specifically for schools. He calls his project Calm Classrooms, and the idea came to him when he was making a set of CDs for children with sleep difficulties.
"The third disc contained what we call heartbeat music therapy, because it has a heartbeat in it," he says. "I did some research and discovered that music with a tempo of 60 beats per minute can calm you to an extent where you're not too relaxed, but your brainwaves are slowed down and you can work really well."
Techniques such as accelerated learning have traditionally used baroque music such as Handel, Bach or Mozart. But Vo Fletcher, who tours the country performing a blend of folk, rock and jazz with Fairport Convention fiddle player Rick Sanders, says there are two problems with this approach.
"The volume levels go up and down, and a lot of students just don't like orchestras."
When he sat down with his 1958 Gibson guitar and composed his Calm Classrooms pieces, he was looking to produce music that had neither the wild fluctuations nor the cultural connotations of classical works. Barely audible, it works at a subliminal level. "It is not meant to be listened to," he stresses. "In fact it's quite boring, really."
The music was tested at schools in Sandwell, in the West Midlands, and the results were so encouraging that Worcester University's department of psychology decided to measure the effect of different styles of music on students' ability to recall information. The study, carried out under controlled conditions, showed that any music was preferable to silence, improving performance to a statistically significant degree. And when compared with classical or pop music, both with and without words, Vo Fletcher's pieces achieved the highest scores of all. Heart and pulse rates relaxed, but minds stayed alert and were able to concentrate more easily.
It was at this point that Steve Lockwood, Dudley LEA's key stage 3 strategy manager, heard of the experiment. Vo Fletcher outlined the theory to him: how a tempo of 60 beats per minute coincided with the brain's alpha rhythms in such a way that the two cortical hemispheres worked independently. They agreed to carry out a full-scale trial at a comprehensive school.
"I'm all for trying out new things and taking a few risks," says Mr Lockwood. And he knew that this attitude was shared by the then deputy head at Pensnett, Sue Bains.
Ms Bains, now the school's headteacher, recalls her first encounter with Vo Fletcher and his unusual brand of ambient music. "We met in a room at the Saltwells education development centre," she says. "He was playing the CD, which was a good move.
"I'm very receptive to music, and it was giving me a nice feeling as we sat and talked. By the time the CD finished, it was as though something making me feel very comfortable in that bare conference room had been taken away.
And I thought, 'Oh, this is stupid'.
"I agreed to take it with me, and when I returned to school, the head's PA and our business manager had had a tough day. So I put the music on, and we listened for a while, and when I turned it off, it had exactly the same effect on them. I then took it home to my husband, a maths teacher who doesn't believe in touchy-feely stuff, and he liked it so much that he wanted his own copy."
When she tested the music in the classroom, Sue Bains was astonished. "The first time I played it was with a group of kids who weren't badly behaved, but were quite talkative. I couldn't believe the effect. They stopped talking, and they asked questions in a much lower tone than normal. When the music finished, all hell broke loose, with people complaining about the fact that it had stopped."
When Steve Lockwood invited Sue Bains and Vo Fletcher to give a presentation of Calm Classrooms to a meeting of Dudley's key stage 3 managers, they played a CD quietly in the background, as an experiment.
Once again, it was what happened when the music ended that was remarkable.
"They began to shuffle around in their seats, take a drink of water and have side conversations while someone was still talking to them," Vo Fletcher recalls. "No fights broke out, but if there had been some chocolate biscuits on offer, it might have been different."
Meanwhile, back at Pensnett, teachers were beginning to return the survey forms that Sue had given them, and in classroom after classroom it seemed that Vo Fletcher's compositions were living up to their name.
Although many of the children said they would rather have their own choice of music playing, most of the staff reported that lessons were indeed much more sedate affairs, enabling them to concentrate less on behaviour and more on teaching. "The kids don't particularly like the music - I'm not going to pretend they do," says Sue Bains. "But there is absolutely no doubt that the calming effect on them is quite dramatic.
"We have even talked about playing it during GCSE exams. We decided against it, because if anyone said it disturbed them, we would have been in trouble. And that's a pity, because some of our children don't turn up to exams for fear of having a panic attack."
At nearby Kingswinford school, where a similar trial has been underway, deputy head Bronwyn Hedley did play Vo Fletcher's music during a Year 9 history test. "I think it helped," she says. "I had it playing gently in the background, and the atmosphere was not as tense as you'd expect during an assessment."
The initial reaction at Kingswinford was mixed, with the school's more able children responding less favourably. But while Bronwyn Hedley has found that the music can be a distraction while setting up lessons and during group work, it has proved useful during periods of individual concentration and personalised learning. "It creates a little capsule," she says, "and when you turn it off, the children look round to see what has happened. And it seems to work better with children who are struggling."
This is reason enough for Sue Bains to carry on with it. "We hope to make a difference to children's lives, and if something helps even one student, then we should have it."
She is also aware of the fringe benefits. Not only do her staff find the music relaxes them during lessons, but she has found it an effective way of defusing confrontations with irate parents. "I can't think of a situation where anger is going to solve a problem within a challenging school and with this music everyone is calmer," she says.
Calm Classrooms is available from Early Birds Music as a boxed set of 10 CDs. For details and prices, visit www.calmclassrooms.co.uk or phone 07801 067386