Over time, most memories slip and fade, or blur into one amorphous string of incidents. But some are savoured so often that they remain fresh and unsmudged, and for me one of those indelible moments was the first time that I saw singer Mohammad Reza Shajarian perform with the Masters of Persian Music, at the Centennial Theatre in 2002.

The evening was memorable for the sheer quality of the music presented, and also because I was one of a handful of non-Iranians in the sold-out venue. But mostly it's Shajarian's presence--both vocal and physical--that remains in my mind. He seemed the calm centre of the ensemble: the other musicians leaned in towards him as if they were playing for his ears alone, and whenever he opened his mouth to sing they instinctively left space for his voice to fill with its incredibly rich, warm, commanding presence. Shajarian's singing that night--and on the Masters' brilliant Without You and Faryad CDs--had the remarkable quality of being simultaneously lulling and invigorating. Listening to him is like being enveloped in a velvety cloak of beauty, but the experience also demands a high degree of attentiveness, so nuanced and intricate is his phrasing.

I've never met a saint, and I have no idea how Shajarian conducts himself in his private life, but on that North Vancouver night the Iranian singer seemed as close to godliness as any human might get. And that he's the real master of the Masters of Persian Music--who play the Orpheum Theatre on Sunday (February 20)--is confirmed by the group's spokesman, Kayhan Kalhor.

"He is the soul of traditional vocal singing, and the best-known singer in Iran," says the kamancheh virtuoso, reached at home in Tehran. "He's been singing for nearly 50 years and has been very famous all that time, but he's never repeated himself, and has always presented a greatness and a power and a beauty with his singing. As you know, it's very hard for musicians to stay like that for 50 years or 45 years. For me, he's a role model. I grew up with his voice, and his singing gets better every year. It's incredible. And now he's 64, but you can't believe it."

Kalhor, a long-time resident of New York City who moved back to Iran two years ago, is a musical genius in his own right. His supple work on the kamancheh, or Persian violin, has been featured in collaborative projects with cello great Yo-Yo Ma, the Kronos Quartet, and bass innovator Bill Laswell, as well as on several albums issued under his own name, and he's much in demand as a composer of film music. But just as he defers to Shajarian's greatness as a singer, he also bows before the compositional prowess of his bandmate Hossein Alizadeh, who plays the long-necked lute known as the tar.

"He's really well known for representing a lot of avant-garde ideas in Persian music," Kalhor explains. "His works are very, very fresh and very different in terms of forms and ideas. Alizadeh's compositions, especially those from the 1970s and early '80s, are milestones that people are imitating here--it's like they're already old styles, because they're so well known. But when he did them 20 years ago they were very, very new, and very surprising, I would say."

And he's equally pleased with the input of the youngest Master, Homayoun Shajarian, a skilled percussionist who has also inherited his illustrious father's vocal prowess. Another memory from the Masters' Vancouver debut: the wave of surprise and pleasure that passed through the crowd when the Shajarians harmonized together on a sinuous Persian ghazal.

"On that first tour none of the audience expected Homayoun to sing," explains Kalhor. "Shajarian has been so great a figure in Persian vocal music that it's often said that he cannot be replaced--but there was his son, producing the same kind of voice. So that was shocking: most people thought he was just there to play tombak with us."

Kalhor notes that the younger Shajarian is an exception in contemporary Iran. Following the Islamic revolution of 1979, many of his country's leading musicians went into exile, and a thousand years of musical tradition suffered a serious, although not irreparable, breach.

"The music is changing," Kayhor contends. "What happens these days is that a lot of musicians don't know about the tradition and they haven't been traditionally trained, but they're trying to change things within traditional music--and usually the product is not very impressive.

"Of course, Alizadeh and me, we're known for not repeating our ancestors," he adds with a laugh. "I think this is a living tradition, and it has the right to change within that framework. But the point that's very important not to miss is that you should be in command of the tradition first."

That these Masters are, and if their Orpheum Theatre appearance is anywhere near as potent as their local debut, Sunday should be another night to remember.