A great party: In the “70s era” room at Mason Bates’s “KC Jukebox” event, Third Coast Percussion ensemble performs Steve Reich’s “Drumming.” (Scott Suchman/The Kennedy Center)

There was a DJ filling a large, resonant space with washes of electronic sound. There were people sitting on sofas against the walls, or standing around talking, or lining up to get a drink at one of the bars, or simply listening to the music. “Lounge Regime,” the inaugural “KC Jukebox” event at the Kennedy Center on Monday night, was less like a concert than a party.

The event was the first in Mason Bates’s tenure as the Kennedy Center’s composer in residence. Bates is a Juilliard-trained classical composer who also performs in clubs under the name DJ Masonic. Even Bates’s orchestral pieces, such as “Mothership,” ­written for the YouTube Symphony Orchestra in 2011, have featured him on beatpad.

Monday’s “KC Jukebox” was a celebration of ambient music, and as the capacity crowd gradually drifted into the performance space — a gallery on the Kennedy Center’s terrace level, enclosed by white curtains — it was no surprise to see Bates, in his familiar gray sweater, at the turntables. The sounds he and the evening’s other DJ, Justin Reed, created could function either as focus or backdrop, something that a busy sequence of projected texts tried to elucidate while the crowd lined up to claim their free drinks at the bar (including a special cocktail made of absinthe and champagne).

The whole evening could have played out there, but Bates has bigger ambitions, a flair for drama and the Kennedy Center’s resources at his disposal. Shortly after the scheduled 8 p.m. start, doors opened at one side of the room onto a low foyer labeled “70s era,” where on one side of the room the four musicians of the Third Coast Percussion ensemble began playing Steve Reich’s seminal “Drumming,” while on the other side an ensemble of principal players of the National Symphony Orchestra gradually began playing La Monte Young’s “Pre-Tortoise Dream Music,” a piece featuring long, sustained droning sounds from flute (Aaron Goldman), clarinet (Loren Kitt), voice (Estelí Gomez) and other instruments.

The performances were excellent. The overlap between the two pieces confirmed that this was not a normal concert in a normal concert space but an exploration of the way we apprehend music. And it was exhilarating to be in a crowded space, enjoying the layers of pleasant stimulation on the ear, sipping a drink and knowing there was more to come.

Indeed, while the music was still going on, a gold curtain rose at the far end of the foyer into the atrium, transformed into a Belle Époque salon complete with gold draperies, upholstered chaises, videos of Paris in the 1920s, two more bars and a grand piano on a high platform, atop which the pianist Lisa Emenheiser, in a feathered period headdress, played “Trois Gymnopedies” by Erik Satie.

At this juncture there was a certain change of focus: The big reveal had taken place and the presentation — including some “Furniture Music” by Satie and a movement of Francis Poulenc’s Wind Sextet — was the closest to concert convention the evening would get. The performances (including the above-mentioned performers along with Nicholas Stovall, Sue Heinemann and Abel Pereira, the NSO’s principal oboe, bassoon and horn, respectively) were both vivid and slightly anticlimactic. After an additional snippet of “Drumming,” the evening’s musical focus returned to the DJ in the entrance hall, while the audience lingered, and talked, and listened, and left.

You could quibble with the dramatic weight of the various parts of the evening. I would have been happy had there been more performances in the ’70s room and more overlapping performances so that different audience members could hear different things. And, as a concept, the evening could be criticized as an incomplete or misleading picture of ambient music, particularly for the implication that the more conventional French salon music was the main event rather than merely a relevant phenomenon.

As an event, though, it was a lot of fun. As a way to illustrate different ways of thinking about music, presenting it and listening to it, it was a resounding success. And as a party, it was great, with Bates now welcoming everyone from the stage, now milling around in the audience, discharging a host’s duty with aplomb. Don’t take it, though, as a sign of things to come: Bates’s next “KC Jukebox,” on Feb. 22, is called “Of Land & Sea,” held in the Theater Lab, and, reportedly, completely different. Don’t miss it.