Phish is back to making its fans happy. (Photo by Danny Clinch/Courtesy of The Fun Star)

Burned out by constant touring, business woes and substance abuse, the Vermont-bred jam band decided that 21 years of wiggly bass fills and trippy guitar solos were enough and pulled the plug. “We’re done,” Trey Anastasio, the band’s guitarist, chief songwriter and de facto leader, told Charlie Rose during an interview. “I’ve never been so sure of anything in my life.”

Or not. Five years later, Phish had a change of heart. In 2009, the band re-formed for a weekend’s worth of gigs at Virginia’s Hampton Coliseum. The comeback stuck, and the quartet has been touring, albeit at a more modest clip, ever since.

On Saturday night, Phish kicked off a two-night stand at Merriweather Post Pavilion, playing to a packed house of googly-eyed, glowstick-waving fans who knew exactly which song was getting played by the first two notes. Even in the dark days leading up to its breakup, Phish could pack the local megadome. But people were grousing about what they heard. There was a consensus — expressed through message boards, fan blogs and print reviews — that the performances weren’t up to snuff.

So far, Phish 2.0 has drawn more favorable feedback.

On Saturday, the band played two 75-minute sets — the first skewing toward the intricate compositions the band favored in its early years, the second heading off into groovier terri­tory.

The goofball jazz of “Reba” and the minimalist ping-ponging ballad “Silent in the Morning” sounded tightly rehearsed.

The jamming, meanwhile, had thinned out. Excursions to the outer limits hovered around 10 minutes rather than 20.

And, as always, there were covers — the Velvet Underground’s “Rock & Roll,” Ween’s “Roses Are Free” and “On Your Way Down” by Allen Toussaint. It’s this musical omnivorousness that has kept the band humming while most of its jam-band peers have faded. To watch a Phish concert is to glimpse fleetingly into a world where genre and style barriers are temporarily irrelevant — where Little Feat, Talking Heads and Frank Zappa can share a stage. A place where it’s okay to vibe-out to a funk-rock take on “Also Sprach Zarathustra,” the “2001: A Space Odys­sey” theme, which Phish dutifully performed.

The recent dash for maturity has had its casualties, however. Some of the group’s oddball antics have been left by the wayside. Anastasio and bassist Mike Gordon have given up bouncing on trampolines during solos. Drummer Jon Fishman used to sing songs into a vacuum cleaner. On Saturday night, he stuck to the kit. He still performs wearing a muumuu, though. There’s only so much you can give up.