IT IS a noun, not a verb. You do not barbecue meat; you smoke it until it becomes barbecue. And it is not a meal so much as a meditative process, perched somewhere between science and art, dependent on reserves of judgment. The science lies in building a fire that will smoulder steadily without flaring, and in constructing a vessel that will bathe the meat in smoke without subjecting it to too much heat. The art lies in the butchering and seasoning. The judgment comes in knowing precisely when a cooking process that may last as long as 18 or 24 hours should end. Barbecue is the art of turning tough cuts tender (“Need no teef to eat my beef” is a popular boast among smokemasters). None of these facts brook disagreement, but here the unity ends.

American barbecue falls into four broad geographic categories—and understand, letter-to-the-editor writers, that this is a crude sketch, not holy writ. In North Carolina pork, either whole hog or shoulder, is seasoned minimally if at all. The sauce, applied at table, varies. In the eastern part of the state it is usually nothing more than cider vinegar, salt and red pepper flakes. In the west it may include a bit of tomato. North Carolina barbecue at its best is as austere and perfect as a bowl of properly cooked Japanese rice. As with rice, however, perfection is exceptionally difficult to achieve, whereas mediocrity is easy. Mediocre Carolina pork will bring back memories of school dinners and premonitions of the nursing home.

Memphis is known for ribs and shoulder, the former often served “dry”, with just a rub of spices, and the latter often served pulled, on a sandwich, with coleslaw as an essential element rather than an option. Unsurprisingly, the ranching state of Texas prefers beef to pork. The brisket is cooked “low and slow” and often served with nothing more than Saltine crackers or white bread, raw onions and pickles. Texas also displays strong German influences, seen in the prevalence of barbecued sausage in the region just east of Austin, as well as Mexican ones, seen in covered-pit barbacoa, traditionally made from cows' heads.

Kansas City barbecue slathers both beef and pork in a sweet, tomato-based sauce: this style of barbecue, probably because it is easiest to do tolerably well and because people always love a sweet sauce, has become the default broad American style. If you order ribs in a chain restaurant in Buffalo or Minneapolis, say, you will probably get them doused in sweet tomato sauce. There are regional quirks throughout the country—western Kentucky prefers mutton to beef or pork, South Carolina's sauce is mustard-based while northern Alabama's is an abomination based on mayonnaise, and Chicagoans display a fondness for rib tips (unwieldy, delicious bits of meat, bone and cartilage). But those are the four main categories.

Barbecue is America's food in the same way that jazz and blues are its music

Yet beyond that rough classification lie deeper questions: what is barbecue? What does it mean? What is its proper venue? These are not mere culinary questions. Barbecue in America, particularly in the American South, is like red wine in Bordeaux or maize in Mexico. More than just something to consume, it is an expression of regional and perhaps even national identity. In “Smokestack Lightning”, a delicious book about barbecue, Lolis Eric Elie explains, “Barbecue alone encompasses the high- and lowbrows, the sacred and the profane, the urban and the rural, the learned and the unlettered, the blacks, the browns, the yellows, the reds and the whites.”

Mr Elie's book, punctuated by Frank Stewart's photographs, is an account of a summer spent driving around America in search of first-class barbecue. It is the sort of book that makes a reader look across the table at spouse and children, and think, “They'll be all right without me for a few months, won't they?” Writer and photographer traverse the rural South and Texas before turning north into Kansas City and Chicago, cities with barbecue traditions shaped by the Great Migration of African-Americans northward from the rural South in the early 20th century. It is a tour of barbecue's redoubts.

Yet even as Mr Elie and Mr Stewart were writing, and photographing, barbecue was spreading from its roots. It is now America's food in the same way that jazz and blues are its music. All were formed from the interplay of African, European and native cultures. Barbecue at its best has a depth and complexity that, say, hotdogs and hamburgers never could; they are Elvis Presley to barbecue's Louis Armstrong. And, like jazz and blues, barbecue is easy to water down. John T. Edge, who heads the Southern Foodways Alliance, gives warning that “there are a lot of people doing a bad job” with barbecue—meaning gimmicks, or superficial gestures, or aiming for mediocrity rather than excellence. In culinary terms it may mean parboiling meat, then coating it with sweet barbecue sauce flavoured with Liquid Smoke rather than taking the time to cook it slowly over a wood fire.

Whereas great barbecue tastes great, even mediocre barbecue tastes pretty good. And mediocre barbecue demands far less time, attention, discipline and labour. It can also be aimed at the broadest possible section of palates, offending few but delighting few as well (for the same reason, one is more likely to hear the music of Kenny G than Miles Davis while on hold). For many years—particularly to those smokehounds trapped in the northeast, or some other benighted and barbecue-deprived corner of the world, forced by cravings to order a rack of baby-back ribs in a middle-of-the-road, non-barbecue establishment, only to be presented with spongy, tasteless meat dripping with smoky ketchup—this danger has long seemed especially perilous. Mr Elie's writing is sharp but markedly elegiac.

Nearly two decades later, however, he has cause—so have we all—for joy. The forces of smoke and time are fighting bravely against prefabricated red sauce and parboiling. Inspired by writers such as Michael Pollan, Alice Waters and Hugh Fearnley-Whittingstall, diners have grown increasingly concerned about the route their food takes from farm to table. There has been a boom not just in organic food but in what Mr Edge calls “vernacular food”. And the country has seen the spread not merely of barbecue, but of first-rate and even inventive barbecue.

Some of the credit belongs to restaurateurs such as Danny Meyer. Mr Meyer is a native of St Louis, whose unique contribution to barbecue is the snoot sandwich, which is just what it sounds like. He opened Blue Smoke in 2002 in Manhattan, an island blessed with many things, barbecue not among them. That absence proved liberating: “In any of the real barbecue destinations of the world,” Mr Meyer explains, “it's heresy to veer from what local tastes have dictated for ever.” But in New York local tastes have dictated nothing, which means nobody (other than finicky expats, who will presumably be too busy stuffing their faces to talk) will object if a restaurant serves Texas-style brisket with a bottle of eastern Carolina vinegar sauce. And indeed Mr Meyer's restaurant, rather than being steeped in a single tradition, is an homage to barbecue's catholicity. Yet befitting its Manhattan location, it has a drinks menu that extends beyond RC Cola and Bud Light. “The worst thing we could have done”, says Mr Meyer, “is to pretend that we were a ‘barbecue joint' rather than a New York restaurant.”

If Blue Smoke is barbecue's greatest-hits collection, Jim & Nick's, a chain of barbecue restaurants, is more “Kind of Blue”: a stylistically coherent album that is not tied to any particular region. Nick Pihakis, an Alabaman who started the chain with his father 25 years ago, boasts that none of his 28 restaurants has a freezer. Their barbecue is hardwood-smoked, low and slow, the right way; the side dishes, biscuits and pie dough are made from scratch. It is neither Memphian nor Texan, but a sort of hybrid of the two, with nods to the traditional southern table as well.

If it ain't got that swing

Messrs Pihakis and Meyer, like smokehounds outside the South, have at some point had to face the question every art form faces: is it authentic? Lauded today, Blue Smoke opened to rocky reviews. What happened, explains Mr Meyer, “was that a small number of ‘gastronauts' felt they had all the knowledge in the world. It was important to them to say ‘I know what authentic is, and this isn't authentic.'” It is easy to defend good barbecue from those who would debase it, but how do you protect a living practice from those who would, in its defence, smother it? Art needs iconoclasts and bold fusions of distinct traditions. Otherwise it stagnates.

Consider the way that music—notably, in America, jazz and hip-hop—developed both distinct regional flavours as well as an overarching hybrid style. Some may prefer, say, New Orleans jazz to the less regional schools of bebop or free jazz, but nobody would seriously argue for the superiority of one over the other. It is comforting to believe in the purity of isolation, and to believe that good barbecue exists only in a remote tarpaper shack, or in obscure blues clubs in Memphis, but it is a fiction. Barbecue, like jazz, develops from conversation, from talking and listening, from eating and thinking. As Duke Ellington said of music, there are really only two kinds of barbecue: good and bad.

Those afflicted by nostalgia for the music of the past can listen to Louis Armstrong or Miles Davis and lament how far the world has fallen. In visual art, too, we have old prints, and in literature we have old books. Food has an advantage that those art forms lack. Every time fire touches flesh it is reinvented: there is nothing to compare it to. The man who had that restaurant, long shuttered, on that corner in West Memphis, Arkansas, where weeds now grow may have been a great cook. His rub might have contained spices unheard of and perhaps his sauce would not have been out of place at the table of Kublai Khan. He may well in fact have been the best that ever was, but all there is to prove it is talk. The past is gone. In fact, it is eaten.