RALEIGH — It wasn’t much bigger than a closet; an alcove off the downtown Marriott Hotel’s third-floor hallway, tucked between the service elevator and vending machines.

But it had near-perfect acoustics and just enough room for five bluegrass musicians – two guitars, banjo, fiddle and mandolin, if the mandolin player stood halfway out in the hall – playing one of many impromptu late-night jams going on in the building Wednesday night.

“It’s the world’s smallest showcase stage,” Joe Newberry of Raleigh, one of the musicians, quipped between songs.

They then started another tune. A passer-by stopped to listen, nodding along. “That’s the real deal there,” he said approvingly before moving on.

Good as the music was, it was hard to stay in one place for long because there was just so much going on nearby. It was tempting to try and be everywhere at once.

Take a stroll through the Raleigh Convention Center during the International Bluegrass Music Association’s “World of Bluegrass” this week, and you’ll come upon multiple clusters of picking circles. Anywhere from three to a dozen musicians will be standing or sitting in a circle, playing away, watching each other’s hands to keep up.

But the real action is happening next door at the Marriott, in the lobby and on the floors designated for all-hours playing. Get off the elevator on the third, fourth, fifth and 17th floors, and you’ll see signs that you can take as invitation or warning: “This is a Jamming Floor. Please Pick your hearts out!”

The Sheraton next door also has jamming and non-jamming floors for the week.

Spontaneous music

Bluegrass has a culture that’s sociable and egalitarian, with instrumentation that makes it eminently portable (no drums or keyboards to haul around, although the upright bass can be trying). That makes it the ultimate spontaneous-jam style of music. Put a bunch of fans and bands together, and in no time they’ll be playing together.

Typically, that happens at outdoor festivals around campfires. But during “World of Bluegrass,” it’s happening indoors and at all hours.

It’s off the grid and not part of the official IBMA program schedule. But this is the heartbeat of the festival, centered on the third floor of the Marriott. Every night, you’ll find people making merry while playing up and down the hallway, and in suites rented by groups including the California Bluegrass Association and the New York-based Grey Fox Bluegrass Festival.

The hotel jams start up not long after dinnertime, picking up steam as the evening progresses and bands and fans come in from their “Bluegrass Ramble” club-hopping. Most nights, the scene goes well into the small hours.

Mary Burdette, assistant director of the Grey Fox festival, said the previous night’s festivities finally wound down about 4:30 a.m. It never would have stopped if they hadn’t finally declared, no mas.

“We pretty much had to say, ‘That’s it, good night!’” Burdette said, laughing, as Jim Gaudet and the Railroad Boys played to a packed room.

At the bar, concierge desk

Downstairs in the Marriott’s lobby as Wednesday night turned into Thursday morning, picking circles had broken out all over – in the hotel bar, conference rooms, even the business center. One trio of really good young players was ensconced behind a granite-top concierge desk off the main lobby.

Zack Bruce sat nearby and watched while unwinding from a several-hour burst of playing – at a showcase earlier in the evening with his Brooklyn-based band, the Birdhive Boys, followed by an energetic jam up on the third floor. A mandolin player, Bruce has been to IBMA before as a fan (bringing his instrument to jam, of course). But this year is his first time as a showcase performer.

That line between fan and performer is blurry in bluegrass, maybe even non-existent. It’s probably a tossup where the music was better Wednesday night, in the showcase clubs or in the hotel hallways.

“The funny thing about bluegrass is that most people who listen to it also play it,” Bruce said. “And the quality of picking here, just in general, is phenomenal. You’ll get together with some guys in a hallway, start picking, and go, ‘Holy crap, why have I never heard of this guy?!’ And it’s someone from Tennessee with a plumbing business. The bass player’s a welder. Another guy’s a dentist. And they can all play. It’s crazy.”

Bruce is 30 years old, trying to make it as a full-time musician. To the bewilderment of his family, he quit his job as an investment banker a year ago to follow his dream.

“My parents and everyone else kept using the H-word about music: ‘hobby,’” he said, pronouncing the word with distaste. “It took me until I was 29 to say, ‘Look, this is what I do, and it’s not just a hobby.’ I do stress about money constantly. But except for that, my quality of life is still 5,000 times higher than even my best day as a banker.

“I was not getting any younger,” Bruce concluded, “and there are worse things than being broke.”

That could probably be the bluegrass player’s credo.

Menconi: 919-829-4759 or blogs.newsobserver.com/beat