His scoldings -- and genuine if less frequent words of praise -- have all been in pursuit of the unattainable: flawless music-making.
Vail's many fans (including me, an alto in his choir the last four years) would argue he has come awfully close. Under his emphatic baton, choruses made up primarily of amateurs and handpicked orchestral ensembles have performed 125 major works, many of them several times, and myriad motets, anthems and masses. Call him elitist, and many do, but Vail cannot abide Christian "praise bands" and their amp-driven religious pop.
Podunk will not do.
"Basses, you're picking any old pitch out of the air!"
In an era when people sit passively listening to music, Vail has persuaded hundreds of amateur disciples -- many of them elderly -- to makemake music. Shunning the spotlight, and without benefit of a lavishly equipped performance hall, he has had a profound effect on the city's choral and sacred music.
Vail -- lean and white-haired, with gold-rimmed spectacles -- is twice the age he was in 1969 when he walked through the doors of St. Alban's.
Woodstock, the rollicking festival in upstate New York, had just reshaped the music scene. Neil Armstrong had walked on the moon. Protests against the Vietnam War were heating up.
Vail accepted the job after being assured that he could put on an annual concert series, as he had at his previous church, St. John's Episcopal (now St. John's Pro-Cathedral). It was a pioneering concept, one that many churches have copied.
Many choristers followed Vail from St. John's, near downtown Los Angeles. One was baritone Scott Rasmussen, a retired pathologist who four decades ago met and married Nina Hinson, Vail's alto soloist.
"When I met Jim, my whole exposure to music went up 10 or 11 notches," Rasmussen said. "Very few people, amateur or professional, get to do as much and as varied music as we did at St. Alban's, from Gregorian chant through Morten Lauridsen."
As for Vail's storied temperament, Rasmussen recalled the grandfather episode of them all: the evening many years ago at St. John's when Vail grew so distraught over the choir's ragged rendition of Bach's Mass in B Minor that he banged down the piano cover and sputtered: "That's it. I'm canceling the performance."
He went to his office and slammed the door, emerging much calmer a few minutes later to find a lone singer: his wife, soprano Barbara Vail. "Where did everybody go?" he asked. A couple of days later, each member received a letter of apology.
"I see the tops of people's heads. This I cannot tolerate!" Translation: If your noses are buried in your music, you can't stay with the conductor's stick!
Born in Los Angeles in 1929, Vail had a precocious passion for music that was nurtured at the First Baptist Church of Los Angeles, a parish with a fine choir and an impressive four-manual organ. As a child, he had a recurring dream that the family piano had morphed into an organ.
Lourene Vail, his 90-year-old sister, vividly recalls the family's cross-country drive in 1933 to visit relatives in Pennsylvania. Fourteen at the time and the oldest of four children, Lourene kept the trip diary.
"Jimmy," 4, the youngest, would be on his knees in the back seat of their Nash sedan, running his hands across a shelf under the back window, pretending it was an organ.
For 40 years as choirmaster of St. Alban's Episcopal Church in Westwood, James Vail has exhorted his vocalists, often in a vexed high-pitched tone accompanied by loud piano-pounding, to mind their sharps and flats.
The USC professor emeritus has spared no section over the decades but has generally reserved his most caustic commentary for the beleaguered basses. ("Somebody is singing 'Lorrrrd' instead of 'Lawd'!")
The concert ahead looms large. It will be Vail's last at St. Alban's because he has decided that, at age 80, it is time to go. Haydn's "Creation" and Brahms' "How Lovely Is Thy Dwelling Place" must be just so. Let no mezzo mangle the high A's, no baritone bleat on a rest. Vail is feeling the pressure, and that means his choristers are too.