WORCESTER — Perfection is a difficult target for bands that place an emphasis on lengthy improvisational interludes, but Phish just about hit a bull’s eye Thursday at the DCU Center during the opening night of its summer tour.

Phish was scheduled for a second sold-out show in the arena Friday.

Beginning the first and closing the second set with the spitfire instrumental “Buried Alive” accentuated the attention Phish paid to overall structure in its sprawling three-hour show. Within each set, Phish built jams around stylistically themed song sequences and made inspired tune selections.

In the first set, for instance, the band put a rustic, honky-tonk shading across the flow from “Runaway Jim” to a cover of the Rolling Stones’ “Torn and Frayed,” the latter galloping along, the former loping. Then it was funk time, first with the hard-edged Son Seals cover “Funky Bitch” paired with a breezy “The Moma Dance.”

And while it was likely coincidental, the band put its most frenetic first-set jams into songs titled after animals — “Ocelot” and “Possum.”

But even with signs of a design at hand, guitarist Trey Anastasio, bassist Mike Gordon, drummer Jon Fishman, and keyboard player Page McConnell sounded limber and looked like they were calling plays in the onstage huddles. McConnell’s “Beauty of a Broken Heart” and Anastasio’s “Nothing” were pretty additions, highlighting songwriting chops to rival the band’s jam power.

Phish took all that was good about set 1 and upped it in set 2. Anastasio generated Zeppelin-worthy riffs in a hard-driving “Carini” to start. A funk fest forged from the psychedelic “Ghost” and Stevie Wonder’s “Boogie on Reggae Woman” formed the core of the set.

The “Ghost” and a reggae-infused “Harry Hood” were huge jamming vehicles, and the band sounded simply inspired as solos passed among members with smooth transitions that would eventually gather into surging ensemble passages.

Phish built in breathing room with the delicate “If I Could” and conjured joyous zeal with Bob Dylan’s “Quinn the Eskimo (The Mighty Quinn).”

For its encore, Phish returned to the Stones’ “Exile on Main St.” for “Loving Cup.”