Otto-Werner Mueller, 89, an old-world maestro whose teaching technique and formidable mien inspired reverence - and no small measure of fear - in generations of conductors and orchestral players, died Thursday evening, Feb. 25, at home in Charlotte, N.C. The cause of death was Parkinson's, said his wife, Virginia Allen.

Mr. Mueller was head of the conducting department at the Curtis Institute of Music from 1986 until his retirement in 2013, and was also a professor at the Juilliard and Yale schools of music. Among his students were New York Philharmonic music director Alan Gilbert and former Cincinnati Symphony Orchestra music director Paavo Järvi.

"He was kind of an institution, and he made an enormous impact, not only on me but on a whole generation of conductors trained at Curtis, Juilliard, and Yale," said Gilbert on Friday just before leading a concert in Leipzig of the Gewandhausorchester.

"Certainly," Gilbert said, "he came to occupy the preeminent position in the world of conducting teaching in the U.S."

"Otto was the greatest preparer and trainer of a conservatory orchestra that I ever saw," said Robert Fitzpatrick, whose tenure as Curtis dean largely overlapped with Mr. Mueller's time there. "The sound he could create with a student orchestra with gestures and coaching just was remarkable."

"He was one of the great orchestra-builders," said David Hayes, who was among Mr. Mueller's first Curtis students and is now music director of the New York Choral Society. "He could get an orchestra to sound from eh to awesome."

He was also an astute judge of conducting talent, even when, in Fitzpatrick's words, that person "couldn't conduct their way out of a paper bag." He would look for incipient talent by gauging a musician's ear and strength of interpretive ideas. One such case of early talent-spotting, he said, was an 18-year-old Miguel Harth-Bedoya, now a busy conductor worldwide.

'A unique skill'

An imposing man who generally used minimal movements on the podium, Mr. Mueller largely concentrated on the somewhat alchemic concept of how gesture elicited orchestral sound. "He was able to craft a sound, and that was not a universal trait," said Hayes. "Some conductors today are wonderful performers, but if you took them away from the Los Angeles Philharmonic or Vienna Philharmonic and asked them to take a lesser orchestra and make them sound better, they are not always capable of doing that. It was a unique skill."

Much of his philosophy could be traced to Richard Strauss, said Fitzpatrick.

"At the end of the war he was 18 or 19, and he sought out Strauss and got a lot of wisdom from that meeting," he said. "He always considered Strauss a very important influence in terms of orchestral sound and conducting technique. He developed a simplified technique, which was very smooth and clear, and he claimed a lot of that came from having seen Strauss conduct and having known what his aesthetic was."

"You should not perspire when conducting. Only the audience should get warm," Strauss famously wrote in his 10 golden rules for young conductors. "Conduct Salome and Elektra as if they were by Mendelssohn: fairy music."

Said Fitzpatrick: "Strauss' 10 golden rules - that was Otto in a nutshell."

Born in 1926 in Bensheim, Germany, Mr. Mueller was appointed director of the chamber music department at Radio Stuttgart. He worked in opera and operetta for the Heidelberg Theater, and founded and conducted an orchestra for families of U.S. military personnel stationed there. He emigrated to Canada in 1951 and worked as pianist, composer, arranger, and conductor for the Canadian Broadcasting Corp., and soon began teaching at the Montreal Conservatory.

He was part of a generation of European-trained conducting pedagogues who came to the United States and have now largely disappeared - Mr. Mueller, Charles Bruck (who had once been Pierre Monteux's assistant) at the Hartt School, and Frederik Prausnitz at Juilliard and the Peabody Institute of the Johns Hopkins University. Perhaps only Gustav Meier, who had been at the University of Michigan and recently retired from Peabody, remains.

The preparation

"One of the things that was hugely important for this generation of conductors was the idea of 'What is the composer telling you?' Seeking answers in the score," said Hayes. "Not that you wouldn't bring your personality to a performance, but [Mr. Mueller] would say that it didn't start with your personality or doing what feels good. It was about being as respectful of the composer as possible."

Said Gilbert: "For me, in addition to what he actually taught and the style and approach he advocated, even more important were the values - the level to which he prepared himself and the level to which he expected his students to prepare."

Hayes recalls what would happen when a conductor did do something not indicated in the score. Mr. Mueller would ask why. "And I can remember people saying, 'I like it,' and he would explode. He would say: 'What do you mean you like it? What does that have to do with anything?' "

It could be embarrassing. Conducting lessons happen essentially in public, at Curtis with either the full orchestra or a smaller lab orchestra. Mr. Mueller's volatility made students quake.

But the experience was useful.

"I didn't like it," said Hayes. "Who really wants to get yelled at like that, and in public? But on the other hand, if you can't take that, good luck when you get in front of a professional orchestra. They'll eat you alive."

He could make a point just by raising an eyebrow with his trademark, one-word warning: Careful. Sometimes he would admonish students for dull phrasing by saying he was so bored his socks just fell asleep. Rehearsals became master classes for not only the conducting students, but for all the players.

"He would do these quasi-analysis sessions in the middle of a rehearsal," said Hayes. "Some found it maddening how meticulous he was and how slow he would go. But the upside was, you understood the structure of the piece and how you fit into the structure, and how to make it sound good."

Surviving in addition to his wife are sons Bernie, Michael, and Peter; grandchildren Christina, Peter, and Sophie; and a brother, nephew, and niece. He was preceded in death by his wife of 56 years, Margarethe.

Memorials in Philadelphia and New York are being planned.