The sunglasses every artist wore onstage at Thursday’s Lilith Fair were more than a fashion accessory – they were as vital as the instruments.

For five of the festival’s eight hours of music, performers played directly into the sun. Singer/songwriter Ingrid Michaelson summed up the misery.

“It’s so hot out here I felt sweat dripping down my legs, and for a second there I thought I pulled a Fergie,” she said, referring to the pop star’s onstage pee incident.

The performers had it easy compared to the fans. After their 40-minute sets they could retreat to cooler confines. Fans had fewer options. Many ditched their seats and scrambled to whatever shade they could find. This made an already undersold Sandstone Amphitheater look even emptier.

All facilities past the second section of seating were closed. Drivers expecting to park in the main lot at the top of the hill were directed to the auxiliary lot. Fans with lawn tickets were upgraded to second-tier seats, while those with second-level seats could move down. As the sun shrank the crowd grew, filling most of the seating, but it was rough going for the early bands.

Vedera fared better than most acts. Sequestered to a tiny side stage, several hundred dedicated fans crowded into the awkward space to hear the local band deliver new gems like “Greater Than” and “Satisfy” in their half-hour set. Vedera was the last of three local acts, which also included singer/songwriters Julia Othmer and Sara Swenson.

Metric was the first band to appear on the main stage, and red flag the fact that holding an all-day event in a venue with little no cover was a poor idea. The relentless sun rendered moot any lighting or special effects. When it was finally dark enough for these tricks to emerge, the video screens captured a static image of the Lilith Fair logo, meaning fans in the back had no close-up view of events all day.

The four-piece indie band’s dark synth pop isn’t built for daylight. Sound problems plagued the first couple songs, but what the atmosphere didn’t kill the temperature did. When you’re sweating just standing still, it’s hard to be convinced to dance. Singer Emily Haines did a robotic dance to the Big Brother-esque lyrics of “Satellite Mind,” and prefaced “Gimme Sympathy” with a bit of Neil Young’s “Hey Hey, My My.” Their set was heavy on last year’s “Fantasies,” but surprisingly did not include their contribution to the latest Twilight film, “Eclipse (All Yours).”

Michaelson had better success connecting with the sparse crowd with her jangly pop. Backed by a five-piece band, Michelson bookended her set with ironic covers, incorporating Lady Gaga’s “Pokerface” into her own “Soldier” and closing with Britney Spears’ “Toxic,” which featured everyone onstage in a synchronized dance. Both moves drew big cheers. In between, she delivered her hit “The Way I Am,” which recalled Regina Spektor’s quirky vocal phrasing, the bouncy “Locked Up,” and new song “Parachute.”

Halfway through the Court Yard Hounds’ set, Emily Robison found herself in trouble.

“This is a quintessential chick song,” she said, intending to introduce Joni Mitchell’s “This Flight Tonight.” The chick the crowd knew, however, was Robison’s main gig with fellow Yard Hound and sister Martie Maguire, the Dixie Chicks. The unexpected burst of delight flummoxed Robison for a moment.

“No, no, not that chick,” she said, trying to recover. “I mean a hippie chick.”

Robison and Maguire released three Dixie Chicks albums before singer Natalie Maines arrived and turned the group into superstars. When Maines bowed out of making new music, the sisters soldiered on. Their sound hews closer to Americana and roots music than the Chicks’ pop country, but suffers without Maines’ feisty spirit. “It Didn’t Make A Sound” featured a nice honky tonk piano solo, and “The Coast” was a pleasant tribute to the sister’s native Texas beaches, but it was too gentle to engage the crowd.

Conversation ceased, however, when the sisters unleashed a furious bluegrass instrumental that had fans on their feet, clapping and stomping along. The set ended with a moment out of “O Brother, Where Art Thou?” when Maguire’s 6-year-old twin daughters joined the ensemble, tentatively playing percussion alongside their mother.

Emmylou Harris is the Mother Maybelle Carter of her generation, collaborating with everyone from Bob Dylan and Neil Young to Ryan Adams and Lyle Lovett. The artists everyone else on the bill respect as legends, she calls contemporaries. Yet even her distinct, wonderful voice wasn’t enough to sway the crowd. As with most artists during the day, the audience was divided between hardcore fans, politely curious listeners and everyone else, waiting impatiently for their act to appear. The ambitious and diverse bill ended up leaving everyone out at some point during the day.

Harris and her four-piece Red Dirt Band leaned heavily on her 1999 album “Red Dirt Girl,” mixing in the good old country of “Wheels” and “Born to Run” (a Paul Kennerly song, not a Bruce Springsteen cover). The most riveting moments were the a cappella gospel arrangement of “Calling My Children Home” and Harris’ own hymn, “The Pearl.”

Harris also shared the day’s best musical moment when she joined Sarah McLachlan on “Angel.” These multi-artist bills should have more of this synergy. Witnessing Harris and the Hounds collaborate on a Bill Monroe bluegrass number, or Haines join McLachlan on “Possession” would have been special events fans would treasure long after they had forgotten the heat and the ticket price.

It wasn’t until Heart took the stage at 8:45 that the fair had its first galvanizing musical moment. The raucous blast of “Barracuda” eradicated the gentle sway of the afternoon and invigorated a crowd that had traded the sun for the moon and was finally ready to move. Sisters Ann and Nancy Wilson delivered a heavy slab of ‘70s rock that had fists pumping and hips shaking. Guitarist Nancy Wilson concluded her acoustic intro to “Crazy On You” with a scissor kick, cueing the rest of the six-piece band. Singer Ann Wilson was in top form, belting the refrain from the Rolling Stones’ “Gimme Shelter” during their own “Even It Up” and easily finessing the dynamics of “Magic Man.”

Lilith Fair founder Sarah McLachlan closed the day nearly eight hours after the first act appeared. The Vancouver native congratulated the crowd for braving the heat and rewarded them with many of her biggest hits, including “Building a Mystery,” “World On Fire” and “Adia.” She needlessly apologized before playing each of her three new songs, but the crowd responded well to those numbers as well.

Here’s a tip to established artists trying to introduce new songs: If you act proud of your new material, fans will be more likely to embrace it. Today’s new song is tomorrow’s sing-along.

The night ended with the gentle lilt of McLachlan’s “Ice Cream” before most of the day’s artists -– including Swenson, who shared a mic with the Court Yard Hounds -– joined together for a joyous romp through Patti Smith’s “Because the Night.”

SETLISTS:

Metric – “Twilight Galaxy,” “Satellite Minds,” “Help I’m Alive,” “Gold Guns Girls,” “Hey Hey, My My” > “Gimme Sympathy,” “Dead Disco.” Ingrid Michaelson – “Soldier” > “Pokerface,” “The Way I Am,” “Parachute,” “Maybe,” “Locked Up,” “The Way I Am,” “Toxic.”

Court Yard Hounds – “Delight (Something New Under the Sun,” “It Didn’t Make a Sound,” untitled new song, “Then Again,” “Fear of Wasted Time,” bluegrass instrumental, “The Coast,” “Ain’t No Son.”

Emmylou Harris – “Here I Am,” “Orphan Girl,” “Evangeline,” “Wheels,” “Born To Run,” “Calling My Children Home,” “Red Dirt Girl,” “Get Up John,” “Bang the Drum Slowly,” “Shores of White Sand,” “The Pearl.”

Heart – “Barracuda,” “Straight On” “Even It Up/Gimme Shelter,” “WTF,” “Hey You,” “Red Velvet Car,” “Alone,” “Magic Man,” “Crazy On You.” Encore: “What Is and What Should Never Be.”

Sarah McLachlan – “Angel” (with Emmylou Harris), “Building a Mystery,” “Loving You Is Easy,” “World On Fire,” “I Will Remember You,” “Forgiveness,” “Adia,” “Out Of Tune,” “Sweet Surrender,” “Possession.” Encore: “Ice Cream,” “Because the Night” (with most of the day’s performers).