Hurwitz, however, is undaunted by such matters. For one thing, he is not troubled by the notion that children will be lost to classical forever if they are not turned on to it early. “To hell with young people,” he told me. “Classical music has traditionally been the preserve of older listeners who have time and disposable income, and that is my audience. Well, O.K., it would be hypocritical of me to disregard young people entirely. I’ve been a classical-music junkie since I was six, so there are certainly young listeners. But what I dislike is the notion that performing-arts organizations should spend their time and energy trying to attract a young audience by making the product ‘hip’ and ‘relevant’ when the population that is most receptive gets ignored. And there will always be old people.”

It’s also true that, if the business is always dying, parts of it always seem to be springing back to life. In recent years, new boutique labels offering unusual repertory have found a niche in the marketplace. Technological advances have made it far easier and cheaper to make a high-quality recording, and the astoundingly high standard of contemporary performance means that a recent live recording can easily rival one of fifty years ago that might have taken three days of studio sessions. A few of the great orchestras, including the London and Chicago Symphonies, have been issuing records and concert broadcasts on their own. The Berlin Philharmonic has a “Digital Concert Hall,” which offers access to both live-streamed performances and an enormous archive of videos going back to the early nineties.

“The stuff keeps coming,” Hurwitz exulted in one of his videos, “and there’s no sign of its stopping.” The problem is keeping the audience alive to it.

Hurwitz’s house, near New Haven, doesn’t appear particularly large from the outside, but when one is inside the place seems to expand, like a child’s dream of a candy store, with room after room of goodies. You pass through a small kitchen and living room (life is clearly elsewhere) and then into a CD-thronged enclave. CDs, some of them in boxes so large they could serve as furniture, appear in the laundry room, in the bedroom, and in a large basement space, the “overflow room.” After renovations that enlarged that space and added shelving on three sides, the overflow room became the always-flowing room, one of the sets for Hurwitz’s videos. Though many shelves are stacked with disks two rows deep, Hurwitz told me, “I pretty much know where everything is.” In the guest room, there are complete scores of Shostakovich’s works, the critical edition of Verdi’s operas, and books of music history and criticism. Hurwitz shares the home with his partner and two enormous cats, who assault many oddly shaped scratching posts placed around the house to keep them from jumping into Dave’s lap when he’s holding forth—or singing, as he often does, in a heimish but accurate interpretation of the music under discussion.

The singing, it turns out, is a consequence of the major labels’ attitudes about copyright. Hurwitz plays excerpts of recordings put out by the independent labels Naxos, which is based in Hong Kong, and Supraphon, which is Czech, but not from the major labels—Universal Music Group, Sony Classical, Warner Classics—which track the use of their music on YouTube and charge creators for playing time. “Aren’t they acting against their own interests?” I asked. His smile vanished. “Large corporations,” he insisted, “are obsessed with preserving the rights of pop-music artists who make them money, and their legal departments adopt a one-size-fits-all approach to protect popular music. They don’t care about classical music at all, and there is no discussing it with them that I have yet found. So I sing.”

Hurwitz’s love for the best performances began when he was six. He was born in Wilmington, Delaware, in 1961, and grew up in Connecticut. As a child, he played various instruments, though none very well. (The tam-tam often seen behind him was loudly struck in community orchestras.) He learned to read music, and he was blessed with a good memory. He earned an M.A. in history from both Johns Hopkins and Stanford, but he does not have an advanced degree in music. After graduation, he worked in the real-estate division of a bank, and he still has a full-time day job in finance. All the while, he has published articles on performance practice in academic journals, pursuing the life of an independent scholar.

By his twenty-fifth birthday, he had finished a book called “Beethoven or Bust: A Practical Guide to Understanding and Listening to Great Music.” The tone is learned but casual. He began writing criticism for audio- and record-review magazines in 1986 and has never stopped. Nowadays, on ClassicsToday, he leads a cohort of critics, including Jed Distler and Robert Levine.

“An insatiable interest in everything to do with music”—that’s what Hurwitz said is necessary to be a critic. “And, second, a healthy dose of insecurity that pushes you to learn all that you can.” Julia Child, he said, was his model for how to address an audience: “Be direct, be honest, have a sense of humor, nobody’s perfect. It’s O.K. to make mistakes now and then.”

If the entire business is not to collapse, dramatizing the best work may be one way of keeping it alive—a way of keeping new interpretations alive, too. And Hurwitz excels at exhortation. Unlike earlier critics, he brazenly turns judgment into competitive play, punching up his discussions with show-business savvy and gamesmanship. What is the best recording of Stravinsky’s “Petrushka”? Why aren’t more people listening to Honegger’s great Third Symphony or Mendelssohn’s intense Sixth Quartet? He will introduce a piece, tell some stories about its performance history, talk (sometimes) about the intricacy of its structure, clown around, perhaps curse the British musical press, which he hates, and then, holding the disks in his hand, he will evaluate a dozen or more candidates. The best Beethoven’s Seventh? The suspense mounts. The best, he says, is George Szell’s performance with the Cleveland Orchestra, from 1959. “Absolutely not!” says this classical nut, but Hurwitz doesn’t mind; he enjoys disagreement, since the love of music flourishes in an atmosphere of passionate attachments and strong distastes.

How do you talk publicly about classical music without making a fool of yourself? No one was more aware of this difficulty than Leonard Bernstein. In a 1957 article in The Atlantic Monthly, Bernstein, echoing the critic Virgil Thomson, deplored the “music appreciation racket”—the mass of commentary, exposition, persuasion, and seduction that flourished until the sixties, in schools, on the radio, and in book after book, much of it dull or embarrassing. In some ways, however, I mourn its passing. At least kids knew something of Bach and Mozart—or played a little of it—before they graduated from high school.

Indeed, I am a product of “music appreciation” myself. Journeying every week to the old Donnell Library, on Fifty-third Street, I would return two scuffed LPs (Beethoven conducted by Toscanini, say) and take out two new ones (Mozart conducted by Beecham). I might also take out a book by Sigmund Spaeth, a man who, for decades, was a rolling mill of classical-music evangelism, in such works as “The Common Sense of Music” (1924), “The Art of Enjoying Music” (1933), and “Great Symphonies: How to Recognize and Remember Them” (1936). In this last, Spaeth, again and again, prints several bars of a symphony with words strung below the notes to help children remember the tune. Thus the gentle repeated two-note pattern with which Brahms begins his Fourth Symphony acquires the Spaethean lyric “Hel-lo! Hel-lo! What ho! What ho!” And then there was B. H. Haggin, a scourge of everyone else’s standards and tastes. Haggin’s “A Book of the Symphony” (1937) was accompanied by a ruler allowing the reader to find a given section of, say, the “Eroica” on a 78-r.p.m. record, the most common format of the time. A ruler to find musical passages!

Once Bernstein landed on broadcast television, in the mid-fifties, such guides looked pitiful. There he was on CBS, handsome and charming as he stood with other musicians on a floor printed with the staves of Beethoven’s Fifth, moving players around to achieve the proper Beethoven sound. A few years later, in 1958, he began broadcasting the “Young People’s Concerts” and continued for fourteen years, vamping and challenging the children (and, more likely, speaking to their parents) with shows on folk music and jazz along with such subjects as “humor in music” and individual programs devoted not just to Bach and Beethoven but to such hard-to-like composers as Sibelius. No one has ever been as good as Bernstein at talking publicly about music, but, in the early, glory days of FM radio, there were enthusiasts who broke the rules. On the beloved, long-gone New York station WNCN, there were d.j.s such as Bill Watson and Fleetwood, who, in the middle of the night, would play the complete “Well-Tempered Clavier” or a whole opera not once but twice.

Hurwitz is a descendant of Bernstein and the mad d.j.s, the heir to the most expressive of musical explainers and celebrants. In his hands, music appreciation has been liberated from boredom. He also exhibits a refreshing receptivity to changes in classical repertory, including the recent growth in programming that features work by historically underrepresented groups. For centuries, it was white men who composed and had their works performed because, Hurwitz said, “they were who they were and had the right connections. Ninety-nine per cent of the stuff they wrote was crap, and no one knows about it or cares about it now. So I have no problem giving some other group a chance. I don’t care who they are. Ninety-nine per cent of what they produce will still be crap, and the best will be just as good as the best historically.” His tendency to prefer recordings over live performance seems to reflect a similarly democratic impulse. “I think one element of classical snobbery is the insistence that live concerts (more expensive and more exclusive) are better or more valid than mass-produced consumer products such as recordings.” How can you tell how good something is until you’ve heard it a couple of times?

Even in the classical-music world, he insists, there are frauds and fools, and, most dangerous of all, arrogant pedants killing the pleasures of music with academic-extremist theories. The period-instrument movement, with its claims of historical “authenticity,” obsesses Hurwitz (and I agree with much of what he says). He’s not entirely against it, but at times he describes it as a commercially driven high-brow con: By the end of the sixties, he said, “people were bored, they wanted a new sound.” A cadre of gifted players (in London, Vienna, and other European cities), egged on by the record companies, saw a way of generating hundreds of albums.