There's vomit all over the stage. The singer, having just howled his way through a heavy rock number which, to the best of my knowledge, was called "Graawwwwllliinnnrrr" has just broken the microphone stand in two and stage-dived into a crowd of drainpipe-trouser-clad scenesters. "I think the bassist has electrocuted himself!" yells the hired security beef at the side of the stage as the crowd charge on to the proscenium. This might be Nashville but the chances of seeing a cowboy hat or hearing a cover of "Stand by Your Man" are looking slimmer by the minute tonight.
"They call it the Nashville curse," local singer-songwriter Matthew Ryan had told me earlier that day over a robust Southern-style lunch of sausage, grits and Bud, served at Jacks' BBQ in the heart of downtown. "It was getting to the point where nobody believed that anything could come out of Nashville unless it had a rhinestone on it. We understand that the heritage is important but if you want to do something that is different to country then it's pretty hard to get anyone to take you seriously."
Later that night as the bouncers aggressively cleared out the crowd and the roadies reluctantly cleared up the vomit it was becoming obvious that Cage the Elephant, the perpetrators of the rock'*'roll carnage I'd just witnessed, were far from the only show in town. There were legions of people attempting to change the image of Nashville as being the musical home to nothing that isn't clad in a cowboy hat and embroidered denim.
The Next Big Nashville music festival is a showcase for more than 130 artists ranging from the howling rock'*'roll of Cage the Elephant to electronica, Southern Gothic balladeers and swampy 21st-century blues. It takes place over a long weekend in September. Not all the bands vomit on stage, though many do seem to harbour dreams of being the next Kings of Leon. They were the first non-country band from the city to achieve global fame – and in the process sparked the realisation among new-music lovers on both sides of the Atlantic that Nashville's country roots had being surrounded by a motley variety of other plant life.
To say that country music is a big deal in Nashville is an understatement of epic proportions. The main drag of Broadway in the downtown of the city is a neon-splattered artery of bars with names such as "Tootsies" and "Hanks" that play sphincter-rupturingly loud country tunes to a braying and greying crowd of out-of-towners on Friday and Saturday nights. Tremendous, unpretentious fun it is, but the lack of young blood is noticeable both on and off the stages. I found it hard to spot anyone without a paunch and who was under the age of 45.
Ignorance of country music in these circles is considered worthy of open mockery: "Y'going to the Grand Ole Opry?" I'm asked by one of a crowd of Southern gentlemen who, it transpired, were on some kind of divorce-party drinking spree.
"I don't know what that is," I replied.
"Hell, are you some kind of Jack-ass?"
I backed off quickly. Country music in the US has superstars who don't even touch the radar over here. Garth Brooks aside, dozens of country acts earn millions and are household names across the American South, though British non-aficionados won't have heard of them. Alan Jackson? Toby Keith? Gretchen Wilson, anyone? They've made scarcely a scratch in the UK but in this part of the world they contributed to the country music genre selling more than 77 million records in the US in 2004.
The shrine for all this, I later discovered, is the aforementioned Grand Ole Opry. This is the venue for, and the name of, the world's longest-running radio show (it's been on the air since 1925 and can be heard on crackly medium wave throughout the US). With the help of a live studio audience, thousands of country music stars, from Dolly Parton to Johnny Cash have performed on a Saturday night programme which, with its utterly atavistic policies, still has live barbershop quartets singing the commercials. Almost unthinkably for the US, the programme only acquired a sponsor in 2004. Appropriately, it was a chain of country-themed restaurants called Cracker Barrel.
It's easy to get a ticket to see the show: just roll up to the Ryman Auditorium during the winter months and the more modern Grand Ole Opry House in summer where admission starts at $36 (£19). But you get a sense of watching a live museum piece rather than something that is still evolving; a feeling exacerbated by the stage backdrop of a cartoon barnyard and an audience of pensioners from out of state, sated on chicken, grits and beer.
It's all very different to the late Sixties, when Bob Dylan journeyed over here to record with Johnny Cash and release a country album homage entitled Nashville Skyline.
It was around the same time that Elvis Presley was using Nashville as his base to record the likes of "Crying in the Chapel" and the grandiose "How Great Thou' Art", which saw him win a Grammy for Best Sacred Performance in 1967. RCA Studio B is the oldest surviving recording studio in Nashville and was where the King recorded nearly all his Sixties hits. Arriving late at night, Elvis and the "Memphis Mafia" would get into their stride at around 3am. The King's demands were legendary: in order to create the right atmosphere for "Crying in the Chapel", for example, every single light in the building was turned off before Elvis would begin to sing.
Since its closure as a studio in 1977, the place has been refitted to its original design. It's located on Music Square West and visitors can take in the ambience on the hourly tours which take place every day (admission is $12.95/£6.80). The centrepiece of the room is a 1942 Steinway. Built for NBC Studios in New York, it hasn't left the room since 1957 (Elvis's attempt to buy it was rebuffed).
"If a song was recorded on RCA session in Studio B, that's the piano that was used," says my guide. I nervously take the battered black leather stool and clumsily bash out my own version of "Return to Sender".
Incredibly, any visitor is allowed to do this if they ask nicely. It's a thrill to tinkle the same ivories as the King – and a much more intimate experience than the gimmicky shopping-mall feel of Graceland, Presley's Memphis mansion.
Strangely enough, Nashville was being graced by Elvis during my visit; Elvis Costello was performing at the Schermerhorn Symphony Center. Opened in 2006 at a cost of $123m (£65m), the main hall is dominated by a huge organ and the number of frosted chandeliers inside wouldn't look out of place in a Russian opera house, yet the feel is still sleek and modern. Large windows allow honeyed shafts of natural light to flood the room.
But it's in the bijou basement of independent, vinyl-heavy record stores such as Grimey's that, most nights of the week, you'll hear artists of a dizzyingly high standard and begin to understand why A&R men from across the country are swarming towards Nashville right now.
The night I left, I was lucky enough to stumble upon a set from Brooke Waggoner. In among all the skinny-jean-clad biliousness, it was something approaching miraculous that the loudest noise I heard during my time in Tennessee came from a piano, cello and violin combination, as Waggoner combined Southern Gothic charm with Rachmaninov-esque explosions of power on her piano. "Thanks so much," she whispers at the end in a cute Southern drawl.
The accent of Nashville may still scream country, but the words and the music are steadily moving away into the unknown.
You cannot fly direct from the UK to Nashville. Plenty of connections are available on airlines such as American or Continental via New York, Northwest via Detroit, Delta via Atlanta or United via Washington DC or Chicago.
Loews Vanderbilt Hotel, 2100 West End Avenue, Nashville (001 615 320 1700; www.loewshotels.com). Double rooms start at $254 (£134), room only.
Ryman Auditorium, 116 Fifth Avenue North (001 615 889 3060; www.ryman.com).
Grand Ole Opry, 2802 Opryland Drive (001 615 871 6779; www.opry.com).
RCA Studio B, 1611 Roy Acuff Place (001 615 416 2001; www.countrymusichalloffame.com).
Grimey's Record Store, 1604 Eighth Avenue South (001 615 254 4801; www.grimeys.com).
Schermerhorn Symphony Center (001 615 687 6500; www.nashvillesymphony.org).
Next Big Nashville (001 615 346 9698; www.nextbignashville.net).
Nashville Convention and Visitors Bureau: 001 800 657 6910; www.visitmusiccity.com