The sunburns have begun to heal. The ears have stopped ringing. But the memories of Bonnaroo 2009 — which saw nearly 80,000 people flocking to Tennessee for a weekend of live performances and varying weather patterns — don’t fade so easily.

This was my fourth time at the festival, and some things never change. There will always be mud. There will always be harsh, unrelenting heat. As the festival wraps up on Sunday evening, a combination of substance abuse and sleep deprivation will inevitably take their toll on Bonnaroo’s most adventurous attendees, resulting in a subdued atmosphere and a sea of passed-out bodies.

Bonnaroo is America’s premier festival, however, and no event earns that title without a steady stream of upgrades. This year introduced a number of new traditions: the presence of golf-cart taxi cabs, a renewed emphasis on environmental activism, and some flashy neon-looking signs (all of which sported the Back to the Future font) marking the festival’s three tents.

THURSDAY

The cab drivers paid their dues on Thursday afternoon, when short bursts of rain turned Bonnaroo into a muddy, Woodstock-worthy mess. Wheels churned in the dirt, sending mud and sludge onto every moving vehicle. Most of the cabbies remained in good spirits, though, particularly a young dreadlocked driver who had converted his cart into a pirate-themed taxi. A sign reading “Arrrr! Tips be good for curing me scurvy!” flapped in the wind as he barreled past us, while his lone passenger – a person clad in a green, full-body ninja suit – hooted at the pedestrians.

After setting up our camp in the rain, we headed into Centeroo to check out the first crop of bands. Janelle Monáe kicked things off in The Other Tent, but we bypassed her futuristic R&B in favor of the White Rabbits’ sweaty indie rock. The Rabbits took a percussive approach to their set, which featured two drummers and occasional percussion from singer/pianist Stephen Patterson. Meanwhile, songwriter Erin McCarley commanded the stage at the cozy Troo Music Lounge, where her band blew the soundboard’s power during their first song. Whoops.

We headed over to That Tent (if you think those names are confusing now, try puzzling things out after three days of Tennessee humidity) to catch the Low Anthem, whose debut album had been released two days prior. The musicians cooled things off with atmospheric folk songs and gorgeous harmonies, but the evening’s strongest vocals arrived during Chairlift’s set. Dressed like a high-school teen queen on her way to the Homecoming Dance, singer Caroline Polachek wailed like the opera-trained offspring of Bjork and Aimee Mann. The band even strutted their way through a cover of Snoop Dogg’s “Sexual Seduction,” although few audience members recognized the song in its slow, Depeche Mode-styled arrangement.

Passion Pit closed out the night as heavy rain soaked everything in its path. The canvas roof of This Tent provided shelter for the crowd, but our own tents weren’t so lucky, and we headed back to the campsite to move them beneath a tarp.

FRIDAY

Mud. So much mud.

As we walked toward Centeroo, making our way past the food booths and t-shirt stands that lined the road, we saw vendors laying straw in front of their makeshift storefronts. Some had resorted to bailing out the biggest mud puddles with a bucket. Few tricks worked, and even though the rain had stopped during the night, the ground squished all the way to the festival gates.

Inside, Kaki King busied herself with a mix of folk songs and guitar virtuosity. We left the gape jawed crowd behind in favor of catching the Animal Collective show, which attracted a larger crowd than most daytime concerts. The band played multiple tracks from their acclaimed Merriweather Post Pavillion, but the show seemed to lack the album’s rhythmic drive, an issue that may have been the soundman’s fault.

Up next were the Yeah Yeah Yeahs, whose impending presence caused a large portion of the crowd to stay in place during the set change. Karen O eventually took the stage in a multi-colored kimono and launched into her patented, charismatic antics: shrieking into the microphone, brandishing it like a sword, and momentarily swallowing it like a banana. Tuning problems forced the group to abandon “Maps” during the first verse, but Karen and Nick Zinner quickly brought out the acoustic guitars in order to do the song “Nashville style.” It was a tender moment in an otherwise raw, raucous set, and Karen’s vocals were gorgeous. Above our heads, some lucky patron watched the band’s encore from a hot air balloon.

Several hours later, the Beastie Boys brought Nas onstage for a performance of “Too Many Rappers,” a new track from the band’s forthcoming record. Meanwhile, David Byrne sported a tutu at the Which Stage, Phish jammed their way through the first of two headlining performances, Phoenix played a criminally short 45-minute set, and Girl Talk kept the party rolling until 4 a.m.

SATURDAY

For the second year in a row, the Drive-By Truckers braved the weekend’s hottest weather and soggiest humidity. Unlike last year, they were joined onstage by Booker T., who added flashes of organ to the Truckers’ songs while also promoting his own release, Potato Hole. The ensemble wrapped things up at 4:15 p.m., just in time for Govt. Mule to take the stage. I’ve never been a fan of Govt. Mule’s long winded improvisation, but you’ve gotta give it to Warren Haynes — the man may be the only jam band leader who can really, really sing.

Bryan Poole, Of Montreal

Indie pop flexed its cute little muscles that afternoon, when Jenny Lewis and Of Montreal performed on opposite stages. Joined by boyfriend Jonathan Rice, Jenny Lewis peppered her set with songs from Acid Tongue and dedicated “See Fernando” to a large, inflatable duck. Even so, her sprightly songs paled in comparison to Of Montreal’s sonic spectacle, which included crazy costumes (seriously — guitarist Bryan Poole looked like Dee Snider circa Stay Hungry), smashed guitars, fog machines, and oodles of off-kilter pop songs.

It was a hard act to follow, perhaps, but the Decemberists managed to keep the spirit going during their follow-up set. The Hazards of Love was recreated in all of its bombastic, operatic glory, and the band’s two guest vocalists — Shara Worden (who sounded like Ann Wilson) and Becky Stark (who looked like the Virgin Mary relocated to the “Lord of the Rings” movie set) — sang everybody else under the table.

Becky Stark, The Decemberists

The Mars Volta played an abbreviated set that evening, which would’ve been heartbreaking if we hadn’t already planned on decamping to the main stage to prepare for Bruce Springsteen. The Boss took the stage at 9 o’clock, flanked by his famed E Street Band and heralded by the cries of an immense audience. The show took awhile to gain momentum — only a small portion of the audience seemed to know Springsteen’s general catalog, and an even smaller portion managed to stomach the eight-minute cowpie known as “Outlaw Pete” — but the rocky start only fueled Springsteen’s fire. He launched himself into the crowd, snatched up all the handmade signs he could find, announced “It’s request time!” with all the zeal of a preacher at a tent revival, and began playing the band’s greatest hits. Best moments: Nils Lofgren’s solo during “Youngstown” (which ended with the guitarist spinning in circles on one foot), a truly standout performance of “Born to Run,” and a guest performance by 18-year old drummer Jay Weinberg, who replaced his Dad midway through the set and turned “Radio Nowhere” into the evening’s fastest, hardest-hitting number. In summary, Springsteen and company killed it.

We soldiered on into the late hours, catching NIN’s theatrical set (which, according to frontman Trent Reznor, was apparently the band’s final show in America ever) and watching Yeasayer amble through a blend of tribal indie rock and hippie psychdelia. MGMT closed out the evening with a surprisingly strong (and surprisingly crowded) show, culminating in a string of hits from Oracular Spectacular and a cover of ‘Til Tuesday’s “Voices Carry” with Caroline Polachek on lead vocals.

SUNDAY

We spent our last day immersing ourselves in hip-hop and country acts — considered strange bedfellows by much of the music-loving world, perhaps, but perfectly compatible companions inside the Bonnaroo gates. Erykah Badu took the stage in a Public Enemy shirt and a bowler hat while Neko Case watched from the wings, and Snoop Dogg played a wide swath of his own hits — as well as a cover of House of Pain’s “Jump Around” — during his subsequent set. Meanwhile, Merle Haggard sounded a bit tired while meandering through an afternoon performance, and Neko Case turned in the festival’s most technically proficient show, even if her siren vocals couldn’t quite make up for a lackluster stage presence. (And let’s not talk about her onstage duet with Triumph the Insult Comic Dog. That was more painful than “Outlaw Pete.”)

After riding the festival’s very own Ferris wheel, we rolled up our tents as Phish closed out the festival with another headlining set, punctuated by Bruce Springsteen’s cameo on “Mustang Sally,” “Bobby Jean,” and “Glory Days.” Our exit from the festival grounds was quick, and we headed back to Ann Arbor during the early morning, dreaming about hot showers and flushable toilets. Bonnaroo is never an easy festival to attend — it’s too hot, too rainy, too exhausting for that — but it’s always been worth the trip.