NEW YORK — Jam-rockers Phish opened a two-night stand Sunday at Radio City Music Hall sounding, not surprisingly, like a band that hadn't played together in five months.

The bandmembers, decked out in black, began with the highly charged "First Tube," an instrumental tune that closes out their latest album, Farmhouse, released May 16. The group played a mix of older favorites and new songs, appearing tentative at times and occasionally out of sync.

Having not played since a New Year's Eve gathering in Florida, its signature sound of intricate arrangements within improvisational soundscapes suffered slightly, but got better as the night went on.

Some fans in the energized crowd were part of Project Phormal, an unofficial movement among "Phish phans" to deck themselves out in formalwear in respect for the historic venue.

Making use of the hall's acoustics, Phish concentrated on the more reflective, quiet tunes from their repertoire. Bassist Mike Gordon, who sometimes gets lost in the mix, sounded full and spunky throughout the night, especially on the night's second number, "Wolfman's Brother."

Notwithstanding, the Vermont band's rhythm section seemed to lag all night behind enthused singer/guitarist Trey Anastasio. This was especially evident on "Down With Disease" (RealAudio excerpt), where the band seemed unable to catch up with the rhythmic gearshifts spearheaded by the guitarist.

Anastasio broke from the band's usual habit of not talking to the crowd, saying, "We are really moved by this whole scene that has surrounded the four of us. Page [McConnell, keyboardist/vocalist] and I came to this hall to see Stevie Wonder, which was a huge inspiration. We feel so lucky and blessed to be able to play here for all of our family, friends and all of you." After a roar from the sold-out crowd, the band closed the set with a charged reading of Anastasio's "Guyute."

An acoustic version of the new Anastasio tune, "The In-Law Josie Wales," had the audience in silence. The band played a rousing version of the Rolling Stones' "Loving Cup" for a second encore and sent the 6,000 fans home singing.

"Tomorrow is gonna be the bomb," said Christian Johnson, 28, of Virginia. "Tonight was cool — it had its moments — but they're gonna bring it hard on Monday [May 22]. Now I need to get a ticket."