Acts hoping to make a splash at South by Southwest — the marvelous, messy, metastasizing music festival celebrating its 25th year in Austin last week — had two options: cannonball or swan dive.

Odd Future, a transgressive young rap collective from Los Angeles, went for the big splash, crowd-surfing across choppy seas of smiling fans on Friday afternoon, many of whom were seeing the blog-
beloved group for the first time.

They greeted Odd Future with a riotous chant — “Swag! Swag! Swag!” — turning a swatch of slang the group uses to punctuate its campy, hyper-violent couplets into a worshipful mantra. (Think swagger, not goodie bags.)

Tyler the Creator was feeling it. The 20-year-old bandleader came jouncing out onstage and instantly threw himself into the crowd. Swag. He threatened photographers. Swag. He flipped off fans. Swag. And in about 30 minutes, he and his crew had summoned the petulance of the Sex Pistols, the zeal of the Wu-Tang Clan and the charisma of both. Swag. Swag. Swag.

James Blake, this year’s other highlight, couldn’t have been more different. Performing on the manicured grounds of the French Legation Museum on Friday, the 21-year-old Londoner sang minimal electronic ballads with a chilling sensuality. And no chanting here. Instead, fans shushed each other during the pockets of dead air that perforated Blake’s most el­egant tunes.

“Limit to Your Love” was the best of them — its deep, otherworldly bass line thrumming like a helicopter lost in some alien atmosphere. And when it kicked in about halfway through the song, something truly magical happened: An actual helicopter flew overhead, its blades thumping away at the exact same tempo.

Does it get any goosebumpier than that? Well, no.

This year, Austin was overrun with similar acts struggling to translate intimate, delicate recordings to the stage — none of which came close to eclipsing Blake. And that was a bummer. Because, in 2011, you don’t go to SXSW to discover your new favorite bands. You go to see if they can do justice to the MP3s you’ve been gorging on all winter. It’s like finding romance online. When you finally meet in real life, things get weird.

Take Chaz Bundick, the South Carolina native who performs as Toro y Moi. His new album, “Underneath the Pine,” is a sweet, nuanced slab of homemade pop made for dancing on beds. But it felt all wrong on the concrete dance floor at Emo’s on Friday, as Bundick had the volume cranked to a level that our neighbors back home would never abide.

Nite Jewel, the stage name of Los Angeles singer Ramona Gonzalez, ran into similar problems. Her best recordings have an enchanting shabby-chic to them, but onstage at Klub Krucial those same bedroom-funk cuts sounded clunky and listless.

As always, there were outliers. Alex Zhang Hungtai, who performs as Dirty Beaches, managed to pro­ject a smoky magnetism in broad daylight on Friday, playing songs that mixed the primitivist punk grime of Suicide with pomade-slick rockabilly riffs. Between reverb-dunked guitar solos that sounded like a series of car accidents at the bottom of a well, he sang, “Ain’t nobody here but me.”

He sure wasn’t singing about SXSW. This year’s festival felt in­cred­ibly crowded, with organizers estimating that it might have been the biggest ever. (Official numbers are still being crunched.)

If you didn’t feel it in the sprawling lines, you felt it on Twitter, where 140-character bursts of enthusiasm could easily convince you that you were always at the wrong show.

The groupthink felt most tangible on Thursday night, when hordes of fans gathered to see the Strokes at Auditorium Shores, a sprawling outdoor park on the south side of town. Once the venue reached capacity, organizers closed the gates, leaving locked-out fans to push and shout and be miserable. (Others saved their breath, summoned their inner Spider-Man and jumped over the chain-link fence. Ahem.)

Inside, the resurgent New York rock quintet made it feel like 2001 again, proving that their best hooks have a timeless cool. And the Strokes weren’t the only marquee act hoping to reboot in Austin this year. TV on the Radio, Foo Fighters and Emmylou Harris each played concerts where they premiered their forthcoming albums onstage — a smart and welcome tweak on the unfortunate, and seemingly unstoppable, trend of bands reuniting to perform their classic albums live.

Never to be outdone, Kanye West closed out the festival with a secret gig at an abandoned power plant in the tiny hours of Sunday morning. It was the rapper’s first major performance since his recent album, “My Beautiful Dark Twisted Fantasy,” posited him as the most ambitious pop star of our time.

He got by with a little help from his friends. Guest turns from Pusha T, Justin Vernon of Bon Iver, John Legend and a showstopping visit from Jay-Z were thrilling, but they couldn’t erase the technical difficulties that marred the set from start to finish. Lyrics were bobbled, cues were missed, and West had to bail on his first take of “Power” after a technical misfire about 25 seconds in.

Fittingly for West — Mr. Zeitgeist — the evening embodied every contradiction that defined SXSW this year. It was both brilliant and boring, invigorating and exhausting, triumphant and disastrous, so much better than the show you were seeing but probably not as good as the show where the band kept stage-diving, chucking water bottles and taunting the crowd. Swag.