It may be notoriously difficult to define, but Sufi philosophy is increasingly popular. As dervishes prepare to swirl into town, Arminta Wallace hears about their spectacular ceremony

Sufi mysticism and global celebrity are not words you would expect to find in the same sentence, but in the post-September 11th US, at least, the 13th-century Sufi poet Jalal al-Din Rumi has become something of a superstar. His work, read by Madonna and Demi Moore, features on a best- selling CD called A Gift Of Love. The video artist Bill Viola quotes him as an inspiration. At a recent DKNY fashion show Rumi was solemnly intoned while supermodels sashayed down the catwalk. A book of his poems, The Essential Rumi, has notched up sales of more than 500,000 copies. The craze for all things Rumi is not confined to the US: go to your local book shop in search of a hardback notebook and the chances are you'll come across at least one Rumiesque offering, complete with quirky drawings and offbeat - even off-the-wall - poetry.

The obvious question is: why? Trying to define Sufi philosophy is notoriously difficult; rather, as one dervish noted wryly, like trying to describe the colour red.

At its most blatantly commercial the Rumi bandwagon is probably just another manifestation of the appetite for instant enlightenment that has, over the past few years, produced all those maddening Little Books Of Calm. But there is nothing gimmicky about Sufism, and its insistence on the power of poetry and music to heal, transform and connect the individual to a universal power has obvious appeal, even in the most determinedly secular culture.

An encounter with Sufi mysticism at its most profound, in the shape of a whirling dervish sema ceremony, can be enriching on many levels, as the virtuoso Turkish reed flute player Süleyman Erguner - who will perform with his ensemble at the National Concert Hall on Thursday - explains. "What we'll perform is a Sufi ceremony, not a concert," he says. "But while some of the audiences get interested in the sema, some others will pay more attention to the music, or some will take the ceremony as a whole, as a spectacular scene. For this reason, having an interest in religious concepts or not is not always important. It is a question that varies from one person to another. But I strongly believe that in some way everybody will be impressed by that spectacular scene."

The best-known exponent of Sufi music in the West is probably the late Nusrat Fateh Ali Khan, the Pakistani qawwali singer whose exuberance, showmanship and spectacular vocal skills made him something of a world-music Pavarotti.

His nephews Rizwan and Muazzam Ali Khan, who perform as Rizwan-Muazzam, have also made high-profile recordings for the Real World label, including a collaboration with the dance and hip-hop merchants Temple of Sound. Sufi musicians come in all shapes and sizes, from Moroccan trance drummers to avant-garde experimentalists in Indonesia, but despite the somewhat overheated image that might be conjured up by the term "whirling dervish", the Turkish Mevlevi tradition is predominantly low-key and contemplative.

The Mevlevi order was founded by Rumi, who fled his native Afghanistan to settle in the southern Turkish city of Konya - both, in the 13th century, under Persian rule. The music of the sema ceremony begins quietly; then, from within the subtle blend of words and music, solo and choral, vocal and instrumental, a momentum gradually develops.

"Verses from the Koran and the poems of Mevlana appear in the beginning of the ceremony," says Erguner. "Hymns addressing God and Muhammad - psalms of praise - come after." Finally the dervishes remove their black cloaks, symbolically casting off death and worldly ties, to reveal voluminous white robes. They begin to turn, slowly at first, then faster and faster. They turn independently, shoulder to shoulder, both around their own axes and around other dervishes, representing Earth revolving on its axis while orbiting the sun; according to mystic teaching, music draws its nature from the music of the spheres and the symmetrical world of abstract numbers.

As they move the dervishes, or semazen, extend their right palms upwards and their left palms down, to allow the power of heaven to move through them and enter Earth. The overall impression is one not of frenzy but of a gravity-defying lightness and a deep calm; for which, incidentally, the explanation may be as much scientific as spiritual. Vertical spinning - think of a child doing a spontaneous pirouette - is said to prompt the release of beneficial beta-endorphins, initiate feelings of relaxed activation and promote right-left brain integration.

On a more immediately artistic plane, of course, the choice of instruments plays a crucial role in the overall effect. The use of the jaunty harmonium gives the Pakistani qawwali a jubilant, almost rowdy quality: the sound of Turkish Sufism is a whisper by comparison. The musicians who form the Süleyman Erguner Ensemble, all accomplished soloists, play a variety of instruments, each of which contributes to the extraordinarily evocative soundscape: the kanun, or zither; kemence, or fiddle; saz, or lute; and tanbur, or frame drum.

At the centre is the ney, or reed flute, whose plangent, breathy sound evokes a sense of primeval simplicity - not unlike that of the flute solo in Debussy's L'Après-Midi d'une Faune - and groundedness. It is probably no coincidence that Erguner comes from a family of ney players - his grandfather and father were the leading performers of their day, and his brother is a highly respected soloist. A teacher at the Istanbul Conservatory who has written the world's first manual of ney technique, Erguner is steeped in the traditional modes of performance but has also developed a uniquely expressive style.

As for the semazen who will do the whirling, there are five of them; one is a student, another is retired and three are from the world of commerce. "When they aren't performing the sema," says Erguner, "they are busy with their own occupations." The blend of dedication and pragmatism seems very Sufi. The philosophy may be difficult to define, but it is characterised by an enviable tolerance and a sophisticated sense of humour - one of Rumi's poems is about a fish that wants a linen shirt.

In the past, as its practitioners strove to steer a middle course between fundamentalist orthodoxy and outright godlessness, these characteristics served Sufism well. And as increasing numbers of global capitalists find something of value in these ancient ideas, it's no wonder its supporters are touting it as a source of spiritual inspiration for the 21st century. On the other hand, as Rumi would doubtless be the first to point out, you can always just lie back and enjoy it.

• The Süleyman Erguner Ensemble is at the National Concert Hall, Dublin, on Thursday at 8 p.m. Süleyman Erguner will talk about Sufism, and give a short performance on the ney, at the Chester Beatty Library, in Dublin Castle, on Thursday at 1.10 p.m. Admission is free, but please let the library know you are coming by calling 01-4070750