"People have always found it implausible that someone who went to Harvard could be so passionate about this music," he says. "Even my family was sure for years that I could have done a whole lot better for myself if I hadn't been so sidetracked by gospel - in other words, been a more conventional academic."
Chuckling and gesticulating in his large, high-ceilinged apartment on Manhattan's Central Park West, the amiable Heilbut takes stock of a life devoted to the twin passions of literature and African-American church music.
He was born 55 years ago in New York, the son of Jewish refugees from Berlin. "People are amazed that a German Jewish atheist would be supposedly the world's expert on gospel music," he says. "My explanation is that everything in America was strange to us. When my brother and I went to baseball games, this was not anything that my parents understood. I was one of the first rock 'n' roll lovers in my neighbourhood in Queen's, and I started going to the Apollo Theatre in Harlem while I was still in high school. Sometime around 1957, I graduated from R&B to gospel. All the R&B people who were coming up then, like Ray Charles, were saying that gospel was where it was at, and the gospel shows were so much better than anything in R&B. I became in thrall - I was obsessed."
Graduating from Harvard in 1966 - his thesis was on DH Lawrence, "a writer whom I've greatly turned against with the years" - Heilbut pursued his love of gospel while teaching at Hunter College and New York University. "Sometime in my late twenties, people were suggesting I write a book about gospel," he recalls. "And because nothing had ever been written on the subject, I had the pleasure of being able to define things. In fact, I defined the golden age of gospel as ending pretty much in 1960/ 1961, and I still think so."
The result of his labours was the hugely acclaimed and still-definitive The Gospel Sound: Good News and Bad Times (1971), the 25th-anniversary edition of which he is currently working on. James Baldwin called it "a very beautiful book, written with love and precision, no pity", adding that "I didn't know anybody knew that much about it, or cared that much, or could be so tough and lucid."
In its beautifully unstuffy exposition of gospel's evolution, and its documentary-like take on seminal figures like Thomas Dorsey, Ira Tucker, Mahalia Jackson and Dorothy Love Coates, The Gospel Sound remains one of the pillars of popular music literature. It has led, in turn, to Heilbut's prodigious work as a producer of albums by his heroes and heroines, most notably Marion Williams, about whom Little Richard claimed "gave me my whoooo!", and RH Harris, founder of the male gospel "quartet" style and mentor to Sam Cooke in the Soul Stirrers.
Given that Heilbut made his name as the foremost chronicler of the gospel world, it is even more surprising that, in the mid-Seventies, he began work on Exiled in Paradise (published 1983), a book which - like The Gospel World - "ran away with itself and became something much more than it was intended to be, which was an account of emigre writers in Hollywood".
Thomas Mann: Eros and Literature is a more or less direct outgrowth of Paradise, and is quite as absorbing about one of the century's most misappraised writers as The Gospel Sound was about Travelling Saints and the "bitter, strong humour" of the sanctified community. Heilbut sets himself the task of rescuing Mann from the role in which he's been cast in the drama of 20th-century literature - that of a pompous, pontificating paterfamilias, the burgherly conscience of German culture.
For Heilbut, Mann's life is "a closet drama ... a tale of profound erotic disappointment" that gave birth to a "merger of perverse fantasy and bourgeois prose rhythms". There is an interesting precedent here in the shape of Hermann Hesse, who defended Mann against a statue-toppling younger generation only too eager to dismiss the author of Buddenbrooks as "too intellectual, too reasonable, too ironic".
American reviewers have focused almost exclusively on the biography's gay reading of Mann's Sehnsucht - the furtive homosexuality that the recently published diaries made more transparent than ever before - but Eros and Literature has even wider implications about repressed yearning and its relationship with art. "I argue from the start of the book that Mann should be seen as a writer as passionate as Proust," says Heilbut. "In fact, he's much less self-hating than Proust, who makes sexuality seem very perverse and life-denying. Mann, perhaps because he's so innocent, is much more tender toward the experience."
Heilbut wants us to see how tremendous Mann's sensitivity is, despite - or even because of - the formidable design and discursiveness of novels like Buddenbrooks and The Magic Mountain. "I use the idea of purloined letters in the book, people looking everywhere for letters that are right there in front of them," he says. "First they deny the thing exists; and then, when you point it out, they say it's obvious. Mann is so discreet, and yet so playful in the way he gives himself away."
For Heilbut, the Nobel prizewinner and father of six was no less neurotic a man than Proust or Kafka, the latter of whom he views as Mann's real literary offspring. "It's about the quietest life imaginable, but internally it's incredibly dramatic. Moreover, he got the worst of both worlds: all the obligations of looking after six children, and all the isolation and frustration of a man who wasn't expressing his desires."
By the cruellest irony of all, it may be that Mann's very courage as an opponent of the Nazis has helped to instil resentment against him - as if he had no right to adopt so Olympian a stance. The loathsome Brecht, for instance, despised Mann as an exemplar of bourgeois liberalism while remaining silent himself about what was happening to Jews back in Germany.
"We have to remember that Mann was the first one to broadcast news of the death camps in 1941," says Heilbut. "And yet, when Mann was hot, it was very much as the wise man, the prophet, and after a while people get sick of that. The point I try to make in the book is that Mann lived long enough to see the reaction, to see people admit, 'We had to fight against him because he was too large'."
Mann himself concluded wearily in 1951 that "it is my fate to be stoned by both sides while striving to serve the whole."
Modernism taught us that our literary heroes must be haunted and alone, free of family ties. Anthony Heilbut knows how hard it is to make Thomas Mann sexy, but he also knows that he deserves a champion to place him alongside Proust and Kafka, Joyce and Conrad, as a modern master.
"I try to demonstrate that, as he said himself, everything he wrote expressed his 'inversion'. This is something very different from the writer of enormous books that people feel they can't tackle. I know that the image of Mann, at least in the English-speaking world, is of someone dry and cold and hard to follow, but if anything I try to show that he's too passionate. Past all the other aspects that interest people about him, finally the most moving thing is his very lonely journey. It was a very painful life."
n Anthony Heilbut's 'Thomas Mann: Eros and Literature' is published by MacMillan, pounds 20. Barney Hoskyns's 'Waiting for the Sun: The Story of the Los Angeles Music Scene' is published by Viking, priced pounds 20