Lorraine Hunt Lieberson; her luminous voice transported listener

When Lorraine Hunt Lieberson sang, time itself stopped to listen. Critics compared her to Maria Callas, but, like Callas, she was one of a kind and incomparable.

The great American mezzo-soprano died Sunday in Santa Fe, where she lived with her husband, composer Peter Lieberson, and dog Coyito ; she was 52. Her family did not disclose the cause of death.

She had suffered from breast cancer, which went into remission in 2001. When knowledge of her illness threatened to color response to her work, or interfere with it, she resolved to keep details of her health private. Nevertheless, her frequent high-profile cancellations in recent seasons caused concern among admirers, and her rare appearances were surrounded with a special aura like the one surrounding the late performances of the British contralto Kathleen Ferrier before she died of cancer in 1953.

Her last Boston performances were of her husband's ``Neruda Songs" with the Boston Symphony Orchestra under James Levine last November, and she toured with the orchestra and the songs in March. Her final performance was of Mahler's Second Symphony with the Chicago Symphony.

Mrs. Hunt Lieberson's unusual career took her to the Glyndebourne Festival in England, the Metropolitan Opera, and many of the major orchestras of the world; in recital she toured with her husband's friend from childhood, pianist Peter Serkin . She sang and recorded baroque music with Nicholas McGegan and William Christie, and made a diverse selection of recordings; her operatic work with maverick stage director Peter Sellars is documented in four videos.

For the last 15 years she could have sung anywhere she wanted to. She preferred to sing music she cared about with colleagues she enjoyed and admired. And she was always focused on new and challenging work by her husband, along with John Harbison , John Adams, and other composers she inspired. Her singing, Peter Lieberson has written, transformed the way he composed.

She premiered several works by Harbison, including his Pulitzer-Prize winning piece, ``The Flight into Egypt," and, at the Metropolitan Opera, his opera ``The Great Gatsby."

Speaking from Tanglewood yesterday, Harbison said, ``What you hear in everything is that tremendous intensity, focus and intelligence, and fascination.

``She was the most prepared, probing, ready-to-go-the-last-mile musician you could ever work with -- she was asking questions beyond where we are."

Born Lorraine Hunt in the San Francisco Bay area, she performed under that name until her marriage to Lieberson in 2000.

An ardent viola player growing up, she began singing in high school musicals and in jazz clubs.

She sang her first opera, ``Hansel and Gretel," in a performance in San Quentin Prison.

She studied singing at the Boston Conservatory and began to sing professionally here in 1984, when she appeared with the Cantata Singers and in a concert performance of Mozart's opera ``Il re pastore" at the Castle Hill Festival. Initially, she billed herself as a soprano and eventually settled into what she called her ``viola voice."

``For all the haunting beauty of her voice, what I valued even more was what she brought to music. At the start it was big and raw and wonderful, and gradually she brought it all under control and it was even more wonderful," said Craig Smith of Emmanuel Music, who conducted her Castle Hill performance. ``I remember in some of the rehearsals for Handel's opera `Giulio Cesare' back in 1985 [Mrs. Hunt Lieberson's breakthrough role], even Peter Sellars got wide-eyed because of the ferocity of her performance."

The Dutch maestro Bernard Haitink conducted Mrs. Hunt Lieberson's celebrated performances in Debussy's ``Pelleas et Melisande" with the Boston Symphony Orchestra in 2004. Yesterday, speaking from Tanglewood, Haitink said, ``Her performance was incredibly beautiful; you could tell how fragile she was because of how fragile she made Melisande. When she sang, you had the feeling that was the way it was supposed to be."

Mrs. Hunt Lieberson's singing was a mixture of the earthy and the spiritual, a mixture that matched her offstage personality. Friends cherish the memory of breathless 90-minute phone calls and long voicemail messages. Speaking to young singers at New England Conservatory in 2004, she said, ``You have to become your biggest supporter. I spent too many years listening to my inner critic who kept me from enjoying my own work. Don't miss out on the fun."

In addition to her husband, Mrs. Hunt Lieberson leaves her mother, Marcia Hunt; her father, Randolph Hunt; a brother, Stan; and a sister, Susan .

Services will be private.