There are great singers, and then there are those few voices that transcend time. The late Nusrat Fateh Ali Khan could not only transcend time, but also language and religion. There was magic when he opened his mouth, a sense of holy ecstasy that was exciting and emotional. It wasn't uncommon even for Western listeners, who didn't understand a word he was singing or follow his Sufi traditions, to be moved to tears upon hearing him.

Ali Khan, who died in 1997 at the age of 48, was a Qawwali, a singer of devotional music of the Sufi sect of Islam. Trained by his father, the master singer Ustad Fateh Ali Khan, he kept up a 600-year family tradition by taking over leadership of the "party" (the general term for a Qawwali group, comprising singer, harmonium and tablas) in 1971, following recurring dreams that he was singing at the Muslim shrine of Hazratja Khawaja Moid-Ud-Din Christie in Ajmer, India (which he would eventually do).

In his improvisations, his voice would soar skyward to heaven, carrying his audience with him. While the core of his work and his life was the Sufi texts, the mystic holy poetry of the spirit, Ali Khan didn't limit himself to that in his career. He was happy to sing the love poems known as ghazals, to perform vocal exercises, and even lend his talents to Bollywood and Hollywood, to range into ambient and dance music. But none of it was at the expense of his soul.

Throughout the '70s and early '80s he released literally hundreds of cassettes-trying to make order of his entire discography would be a nightmare-and his reputation grew, not only in his native Pakistan, but also internationally. The year 1985 proved to be the turning point for him, as he appeared not only at the WOMAD festival in England, but also had his performances in France recorded for an epic five-CD set that perfectly illustrated the qualities of his art. The songs stretched out, allowing Ali Khan to show his genius for extemporization, turning a sound, word or phrase over and over, examining it, flying with it, before releasing it and moving to another, using them all as enlightenment for the soul, a prayer and devotion. At his best, and his best seemed to occur often, he was like a bird, swooping and rising, his voice as free as the sky.

After Paris, the momentum gathered. He signed with Real World Records, which meant that for the first time his records would have high-profile international distribution, and released Shahen Shah, whose title came from his nickname. It wasn't hardcore Ali Khan, but lighter and more melodic, a disc that seduced those who hadn't heard him before.

From there he released the groundbreaking Mustt Mustt, working with producer Michael Brook, and having the title track (which means "intoxicated") remixed into a dancefloor hit by Massive Attack. Suddenly Ali Khan was big news outside just ethnic circles. A second Brook/Ali Khan meeting, Night Song, built on what they'd created for an album of gorgeous fusion.

For the rest of his career he'd alternate between albums that featured his traditional work and what he termed his "experiments." He contributed to the soundtrack of Dead Man Walking, collaborating with another icon-Pearl Jam singer Eddie Vedder-on two tracks. To Ali Khan, while his heart was firmly in Qawwali music, nothing was outside the box, and every opportunity to discover more music and take chances was to be relished, not reviled. He stayed busy until the final months of his life, performing, recording, meditating and teaching.

He reached the stage in the summer of 1997 of needing a kidney transplant, and was on his way to the United States for the operation when he died of renal failure in London.

His legacy lives on prominently in his relatives Rahat Fateh Ali Khan, and also the Rizwan-Muazzam Qawwali Group. But however good they may be, whatever they absorbed and inherited from the Master, there was only one Nusrat Fateh Ali Khan.