How unprecedented is it for a world-renowned jazz artist to be heckled — let alone frequently — during a concert?

Until Pat Metheny’s Saturday night solo guitar performance at The Magnolia in the San Diego suburb of El Cajon, being heckled while on stage was something this 20-time Grammy Award-winner had never encountered. And understandably so, since heckling at jazz concerts is as unprecedented as stage-diving at symphony orchestra performances or mosh-pits at book signings.

So, it was an unfortunate first — for Metheny and his otherwise attentive and appreciative audience — that his near-capacity concert here was repeatedly marred by a heckler. What transpired might have qualified for an especially skewed “Saturday Night Live” skit (if jazz was ever actually on the show’s radar).

A quick Google search for other instances of jazz artists, legendary or otherwise, being heckled during performances brought up no results. In this writer’s decades of attending concerts, not one instance comes to mind of a jazz artist enduring the kind of inexcusable behavior to which Metheny was subjected.

A periodic good-natured quip from an attendee? Sure. Requests for a favorite song? Of course. But repeated mid-song interruptions, apparently to voice displeasure with the music? Never.

“This is a first,” Metheny told the audience. He added that — in his 50 years of touring — he had never been subjected to such heckling and had no idea how to deal with it.

That is not surprising.

Whether performing with a band or on his own, Metheny’s impeccably crafted music inspires listeners to savor the skill and sophistication of his work, its fire and finesse, and the emotional and stylistic depth and breadth he brings to concert stages nightly.

On Saturday, it was unclear what the heckler and his female companion, who had front-row center tickets, expected to hear. But his loud jeers were jarring and dumbfounding.

Metheny — as I wrote in my Sunday Facebook post on which this article is based — was clearly taken aback. At first, he made a reference to coughing by audience members being audible on stage and asked that people try to time their coughs to coincide with musically appropriate moments. Alas, his wry metaphor was lost on the oblivious heckler in the front-row.

After the heckler disrupted an exquisitely delicate version of “Message to a Friend,” Metheny performed “Zero Tolerance for Silence,” a wonderfully abrasive, almost industrial, sonic hand grenade of a piece. Its irony-filled title seemed like a perfectly timed riposte to the unruly attendee in the front-row.

Metheny’s subsequent reference to maybe asking Jerry Seinfeld how to deal with a heckler also fell on deaf ears. This heckler seemed to have a one-track mind — and that track clearly did not include paying attention or demonstrating even an inkling of consideration for the performer or other concertgoers.

About half an hour before the concert’s conclusion, the guitarist grew so frustrated that he stopped mid-song. Metheny, 69, told the audience he had never experienced such disruptive behavior in his half-century as a performer.

He also said that — with each note he played Saturday night at The Magnolia — he wondered and worried when the next interruption would come. Metheny asked the audience: “What should we do?” Yells of “Kick him out!” filled the air.

A security guard then appeared, about 90 minutes too late, and escorted the heckler and his companion to the left exit door closest to the stage. The heckler shoved his female companion so hard, she nearly lost her balance.

That Metheny persevered and somehow still delivered an often-sublime performance is a testimony to his artistry and professionalism. That anyone with the good taste to attend one of his concerts would behave so badly — let alone pay good money for two front-row tickets from which to behave so badly — is mind-boggling.

As of this writing, my Sunday Facebook post has garnered more than 150 responses. Some are from people who were at Metheny’s Magnolia performance. Others are from people who did not attend but were no less appalled, and outraged, that such boorish behavior took place at the expense of so many.

“There’s always one idiot at a concert,” the man seated next to me muttered in response to the heckler. In this case, sadly, that idiot was front, center, and tolerated for far too long.