Youssou N'Dour's new album began as a Ramadan project. Now 'Egypt' presents a new face of Islam to the West, he tells Arminta Wallace

'An arresting tenor: a supple voice deployed with prophetic authority." That's how the New York Times described the voice of Youssou N'Dour. It was, of course, talking about his singing voice. When he's speaking - especially when he's on somebody else's mobile, somewhere in the Paris public-transport system, having embarked on a hectic schedule of live performances that will bring him to all corners of Europe, including Vicar Street, in Dublin - his voice comes across as muffled, slightly American- accented and surprisingly deep.

It is just one of N'Dour's many voices. For most people in the West his are the silken vocal cords on the 1994 hit Seven Seconds, the trilingual duet with Neneh Cherry that turned him into a global star. Listen to some of the early recordings made in his native Senegal, though, and you'll hear a different N'Dour: raw, urgent, energetic. Listen to Nothing's In Vain, his 2002 album, and you'll hear a confident, mature artist who has crafted a superb fusion of his African musical roots with a host of outside influences.

And if you listen to his new album, Egypt, you'll hear yet another N'Dour. It's unlikely you'll ever have heard anything quite like it. A collection of songs that pay tribute to the saints of Senegalese Sufism, Egypt is a work of consummate beauty. The songs are playful and affectionate, the instrumentation a sophisticated blend of his own band - complete with kora player and Senegalese percussion - and a 15-piece Egyptian orchestra led by the composer Fathy Salama. This is neither the downbeat, restrained tonality of the dervish sema tradition, nor the cheerful rowdiness of qawwali, but the voice of an Islam the West is totally unfamiliar with - and that, as N'Dour explains, is the point. "I began this project during Ramadan in 1998, as a personal exercise just for myself," he says. "I never intended to release it. Then I played it for some of my people, and they said you're crazy, this is for everybody." It was all progressing nicely until the autumn of 2001 and the atrocity of September 11th - not a good time to release an album of Islamic music in the wider world. "I waited and waited and waited." And now the time has come? "My religion is important to me," he says, simply.

N'Dour's religion preaches, as does the album, tolerance, ecumenism and celebration. He was born into a Muslim family in Dakar in 1959. His father was a mechanic, his mother a respected singer from the griot caste of oral storytellers. Young Youssou began to sing at family celebrations and, when he declared his intention to pursue a career in music, was sent to study the subject at the École des Arts in Dakar. By 12 he had appeared on a radio talent show and made his professional début, with a theatrical troupe. He began to hang around nightclubs, got gigs here and there and, in 1977, founded the band Super Étoile de Dakar. It quickly became a Senegalese supergroup, almost single-handedly creating mbalax, a wildly energetic dance music whose complex rhythms, lopsided cycle of repeats and sudden changes of emphasis made it an unlikely candidate for global popularity.

Then a Senegalese taxi driver who was living and working in Paris took a hand in the proceedings. "My first European performances with the Super Étoile were organised in 1979 by my countryman Moustapha Ndiaye and people he knew in other countries," N'Dour has said. "They were not show-business professionals, but they found ways to make concerts happen for us. Without Tapha Ndiaye and the others I probably never would have performed outside of Senegal. My international career probably would not have existed."

Instead word spread fast. The 25-year-old was invited to a series of concerts called African Nights in London in 1984. Peter Gabriel was in the audience. Within five years N'Dour was touring with Sting and Stevie Wonder.

Some would say that, in climbing to the top of the international tree, N'Dour lost his musical way. His album Joko, from 2000, the first he had released outside of Senegal in six years, appeared to signal a change in direction - "if you don't know where you're heading any more, go back to where you come from" was the opening line of the opening track - as, more recently, did Nothing's In Vain.

How does he remember the years of MOR stardom? Does he have regrets about going down that road? "It was a magical time," he says, without hesitation. "Just yesterday I was listening to one of my albums from that period, and it moved me very much. So, you know, I'm not saying I've changed direction or that one kind of music is better or anything like that. It was a magical time. I met many, many interesting people, which is what always interests me most. And, looking back, each album is like the work of an architect designing houses. Each house is different, but you can see the trace of his hand all the same."

There is no mistaking the trace of his hand on the new album. Though drawing heavily on musical material traditional to the Sufi communities of Senegal - N'Dour belongs to the Mouride community - the songs on Egypt are original compositions developed in collaboration with Salama. "The content is already something we know," says N'Dour, "but we worked together, and with some other people as well, on the melodies."

On the album his voice is at its delicate, effortless best, but perhaps the most striking aspect of the music is the way the songs repeatedly invoke the most revered figures of Senegalese Sufism. These include a 15th-century Algerian saint called Abu Abdallah Muhammad ibn Yusuf al-Sanusi, author of a seminal Muslim treatise on the unity of God that is also a discussion of the relationship between the outer world and inner spiritual reality; Limamou Laye, a Senegalese incarnation of the messianic figure in Islam, who was tried for sedition by a French colonial tribunal in 1887 and acquitted on the grounds that, according to the judge, "far from preaching subversive doctrines this marabout" - or Muslim monk - "is teaching . . . only the fear of God, obeying one's parents and loyalty to family"; and the founder of the Mouride Sufi community, Sheikh Amadou Bamba, whose life of asceticism and erudition led him to develop a spirituality that ascribed a particular religious dignity to physical work.

The unabashed celebration of such esoteric saintliness sounds odd to Western ears, but if N'Dour's lyrics are to be believed Sheikh Bamba, in particular, has been a big influence on his life. "He has written a mountain of poetry which says many beautiful things about the life of the prophet Muhammad and about how we should live. Religious music doesn't have to be sad, any more than religion itself does. It can focus on happy things. Positive things."

In Senegal religion is seen not as a private matter but as a system intimately linked to such notions as community and social justice, and in that respect, N'Dour says, all his songs have messages. The title track from Set, his 1990 album, for example, inspired a kind of social movement in Senegal. The Wolof word set means clean or pure, and the song became a mission statement for children in the ghettos of Dakar, who took it on themselves to clean up their neighbourhoods, clearing away illegal dumps and cleaning up neglected water supplies. More recently he has been involved in a project, linked to the Joko album, to provide more Internet-access centres in Senegal, in an attempt to create a computer-literate generation that can take full advantage of information technology and its attendant prosperity.

But then, back home, N'Dour is himself revered almost religiously, his name scrawled on the side of fishing boats and taxis, bicycles and school walls. Whatever he does on the international scene will only enhance that - including, perhaps, the release of an album such as Egypt, a potent political statement from an artist patentlyunhappy about what is going on in Iraq and elsewhere.

Does he have any plans for a follow-up album, whether in the same vein or in total contrast? "I haven't thought about that yet," he says. And, after a pause, "I'm still a little busy with this one."

Youssou N'Dour and the Fathy Salama Orchestra are at Vicar Street, Dublin, on Sunday, as part of the Routes in Rhythm series. The album Egypt is on Nonesuch