To 31/2 decades of Philadelphia Orchestra listeners, he was the mysterious Swan of Tuonela, the soul of serenity in Dvorák's "New World" Symphony.

Louis Rosenblatt, 81, an English hornist of unfailing equanimity and expressivity, died yesterday at Abington Memorial Hospital after enduring several bouts of cancer, said his wife, Renate.

English hornists begin life as oboists, and it was so for Mr. Rosenblatt, whose destiny with the more throaty member of the oboe family seemed more like the instrument's pursuit of him than the other way around.

Born in South Philadelphia, he spent his early years in Coney Island and Harlem. His parents moved back to Philadelphia when he was a teenager, and he started studying oboe at South Philadelphia High.

He took lessons with John Minsker, English hornist of the Philadelphia Orchestra, and then, upon enrolling at the Curtis Institute of Music, with Marcel Tabuteau, the orchestra's renowned first oboist. He graduated from Curtis in 1951.

He started out on his oboe career as first-chair player in the U.S. Army Field Band for three years, but somehow the English horn kept calling.

He became English hornist in the Houston Symphony, then the New Orleans Symphony. He next landed a job as assistant first oboist with the Philadelphia Orchestra, in 1959, and just as he was getting started, his old teacher Minsker abruptly quit.

"Minsker saw the schedule for that season and found out he had to do Swan of Tuonela again," said Renate Rosenblatt, "and also the Honegger Concerto da Camera for Flute, English Horn and String Orchestra, which he had never played, and said, 'To hell with it, I'm quitting.' My husband was the extra player, and [conductor Eugene] Ormandy said, 'You're going to play the English horn.'

"He really didn't want to play the English horn. He was a superb oboist."

He was also an influential teacher. He taught at Temple University for nearly five decades and at the Boston University Tanglewood Institute, and he substituted at the Juilliard School, yielding students who played in the Philadelphia Orchestra, Pittsburgh Symphony, St. Louis Symphony Orchestra, and Metropolitan Opera orchestra.

He also briefly moonlighted as a music critic. When the Marlboro Music Festival was getting started, the local paper, the Brattleboro Reformer, agreed to run music reviews if the festival bought ads - and if Marlboro supplied the reviews itself.

So Anthony P. Checchia, its administrator, turned to Mr. Rosenblatt - a resident artist at Marlboro himself - who wrote under the nom de plume H.D. Semiquaver (hemidemisemiquaver is the British term for a 64th note).

Rudolf Serkin, the pianist who ran Marlboro, was mystified.

"Serkin knew the newspaper, and he couldn't understand how a review of this sophistication would appear," said Checchia.

Mr. Rosenblatt probably could have turned in prose of equal sophistication in Yiddish (his first language), Japanese, French, or Italian, being fluent in them all.

He retired from the orchestra in 1995 after 36 years, and was admired, if not always emulated, by his colleagues for quitting at the top of his game. Few people knew how nervous he was as a performer. And yet he was frequently in the spotlight, performing concertos by Skrowaczewski, Persichetti, or Fiala, or works with prominent parts, like Copland's Quiet City.

Once he tripled on English horn, oboe, and oboe d'amore on a single program, in 1980, with the Concerto Soloists.

"He suffered terribly from nerves, and as he got older and realized how many things could go wrong, he just didn't enjoy playing anymore," said his wife of 56 years, a composer and pianist who would often write his cadenzas or edit parts.

Mr. Rosenblatt died yesterday, she said, listening to a Handel oratorio on an iPod programmed by one of their sons.

"He had this beautiful music in his ears," she said.

Besides his wife, he is survived by a brother, actor Len Ross; sons William and Richard; and two grandchildren.

No service is planned, but a memorial will be scheduled, his wife said.