The sound is indescribable. But I'll try. Imagine an average-sized commercial aircraft revving up in your living room. As the continuous bass roar makes your insides vibrate, somehow, just above it, there are two musical notes - called harmonics - that alternate with each other. The sound has been compared to the music of the spheres or tinkling, flute-like angels' voices.
When I heard Mongolian overtone chanting for just a couple of minutes I was so moved it literally took my breath away. To be able to produce it is an exhilarating experience. One of the tricks is in changing the shape of the resonating cavity (mouth to you and me), which takes practice.
The person producing the chant was Jill Purce, a woman who's probably had more practice than almost anyone else in the West. For the last 25 years, she has been on a quest to re-enchant the world - in all senses of the word.
Chanting has an undeniable magical, mystical component to it. But you don't have to be into any particular "ism" to do it. As she puts it, "I wanted to find a way in which people could participate and come together to chant without being card-carrying Buddhists or anything else."
The fundamental question is, if there isn't a religious or spiritual spur to do it, why do it at all? Purce, who runs workshops all over the world and writes about different forms of sacred chant and singing, explains it with a mix of science and spirituality that makes her such a compelling proselytiser.
"It appears that chanting stimulates the release of endorphins, along with other chemicals in the brain, leading to a heightened awareness and calm," she says. "It allows you to integrate body and mind, bringing about a state of order based on your own geometric proportions. This leaves you feeling attuned, blissful, meditative, transformed." Some forms of chanting are even reputed to have healing powers.
Jill Purce runs workshops and retreats in other forms of chanting, attracting everyone from children to octogenarians, from professional singers to healers to people who haven't used their voices for anything beyond a mumble since being told as children that they couldn't sing.
But there's another reason for a growing number of people to be flocking to Jill Purce's chanting workshops and to others peppered around the country. Put simply, it's that people get a buzz from singing in a group - a rare activity as we in the West sit on the edge of a millennium that has become largely godless and increasingly isolating.
The choral singing of the past is all but defunct as church is no longer an outlet for most people to bring their voices together in unison. Neither is the pub sing-along or even gathering around the piano at home a feature of many people's lives anymore. With the exception of football season-ticket holders who can belt out chants regularly from the terraces, it's conceivable that the majority of us will live the whole of our adults lives without singing a note except on occasions that force us into places of worship.
The simple fact is that being in a group singing together can be a pleasurable, even liberating experience, no matter what sounds come out. While Mongolian overtone chanting takes some hours to perfect, everyone can let rip with simple tunes.
Even me. One Sunday evening, I found myself in a room in a quiet residential street in St Albans with about 25 others. In a large circle we sat, people of all ages and walks of life, toddlers, teenagers, one or two women in their sixties, lots of women in their thirties and forties and as many men as you could count on the first four fingers of one hand. Some looked as straight as arrows, others were nouveau hippy. There were the gold-loafered and a smattering of earth mothers. And there were some in between, sporting long strings of wooden beads to offset their Marks and Spencer jumpers. Inside the circle was a large round tray on which sat a circle of tiny candles, giving off a soft, warm glow. We were all there to chant.
Everyone had something to shake or bang to accompany the chants. Maracas were thrust into my hand as we began "Wichita doo - ee - a; Watcha tanaya haya hay." It's a Native American chant and we sang it over and over . . . and over again. It felt like hours but was probably about four minutes. I didn't have a clue what it was about until at long last Ian Godfrey told us: "It's about a river somewhere in the States."
"It's in Kansas. Wichita, remember" gently interjected Andy Cox, a maths teacher who runs the sessions with Ian. He went on to tell us that it's about life being like a river, going through traumas like a river goes through rapids.
From there, we were into a Sanskrit chant for the goddess Shiva, then a bit of doggerel to the tune of Fr re Jacques about life being like a melancholy flower - or was it a cauliflower? - then back to the Native Americans and a chant about how the earth is sacred to "my people". Some people swayed or danced on the spot. I banged a Native American hand drum (made in Britain from deer hide) that had been offered to me after I managed to misplace the maracas.
I ask the woman next to me why she's here and what she gets out of chanting. She was told about it by her yoga teacher and brought her nine-year-old son along with her. "It started off as my thing," she says "but now it's definitely his. He loves the drumming." Still, she gets something out of it too; she says she feels uplifted and grounded at the same time. It sounds vaguely like a contradiction to me, but she looks positively glowing.
Ian, who's been chanting for 19 years says, "it creates a positive energy between people. It's similar to chanting in a football crowd or a church choir in the sense of uniting people." He and Andy choose mainly Native American material that focuses on "the unity of the living world, on the environment and on us being part of it." He's taken workshops into prisons, where they've been enthusiastically received.
"What we do isn't tied to a particular dogma or religion," says the 50-year-old development manager for a major department store group. "It's multicultural and without boundaries. The energy it creates is universal." You don't have to be a singer to join in, either. "It's not asking people to have incredible singing voices and there's no emphasis on getting it tone perfect. It's about having fun and being relaxed." If there's a living, breathing example of the laissez-faire nature of the workshops, it's Ian himself. The man's tone deaf.
Clearly, the chanting that Jill Purce and Ian Godfrey are talking about are qualitatively and generically different from each other in fundamental ways. But they are both giving participants something that they're not getting elsewhere. At its most basic level, it's a sense of creating something with other people by bringing their voices together. But at a deeper level, it can be a vehicle for moving the spirit.
I have to come clean to you. At Ian and Andy's session, my spirit wasn't moved an inch. try as I might, I don't think of the moon as my sister and the sun as my brother. And although I take my bottles diligently to the recycling bin every few weeks, my oneness with the earth is not one of my more driving forces, I'm ashamed to say.
But in different circumstances, who knows?
Jill Purce can be contacted at: Inner Sound, 8 Elms Avenue, London N10 2JP. Tel: 0181 444 4855. She runs introductory weekend workshops at Regent's College, Regent's Park, every month. Ian Godfrey and Andy Cox run chanting sessions in St Albans on the second and fourth Sunday of every month. Contact Ian Godfrey at 52 St Agnells Lane, Hemel Hempstead, Herts HP2 7AY