Roots-rock musicians guest with each other's bands and form spinoff groups about as often as they change chords, their collaborative spirits bubbling into all those music-venue marquees reading "… and Friends."

Trigger Hippy, composed of Black Crowes drummer Steve Gorman, ex-Crowes guitarist Audley Freed, bassist Nick Govrik, singer Joan Osborne and Sacramento singer/multi-instrumentalist Jackie Greene, distinguishes itself with its wealth of singing talent.

"It has been (great) to have someone who is such a strong singer in the same band," Osborne, speaking by phone from her home in New York, said about working with Greene. "I don't know too many bands who have that dynamic of a male and female singer."

Greene said Osborne, whose biggest hit "One of Us" belied her more soulful overall sound, challenges him vocally.

"The woman's got pipes. What can I say?" said Greene, performing Tuesday night at Ace of Spades with Osborne and the rest of Trigger Hippy.

"You have to really be on your best game, because she can flatten you. … I like to be challenged and get inside the song and really sort of perform it the best we can do it, and she sort of demands that of everybody."

Greene said he also enjoys "that kind of sexual tension of a male-female duet," noting his own affection for Marvin Gaye-Tammi Terrell collaborations. "To me, that's entertainment."

Trigger Hippy has yet to release recorded music, but videos of live performances (á la www.triggerhippy.net), especially of the earthy duet "Heartache on the Line," showcase Greene and Osborne's smooth yet powerful blend of voices.

"They are just sympathetic to each other naturally as singers," Gorman said. The Nashville drummer spearheaded Trigger Hippy, which morphed and gained seriousness over the past few years.

A previous version contained Widespread Panic guitarist Jimmy Herring. When he dropped out because of other commitments, Gorman urged Greene, who had played gigs with the Black Crowes, to come to Nashville to see how things jelled.

"We figured this is going to be really, really cool or it's not going to be," Gorman said by phone from Nashville.

A merging of sensibilities has "been pretty effortless," Gorman said.

Greene and Osborne shared a Grateful Dead connection, since Osborne toured with the Dead and Greene with the bands' bassist Phil Lesh.

The band's collective musical affinity reaches farther into the American songbook.

"We all have this kind of rock 'n' roll spirit running through us, but (Govrik) is a really soulful dude, and Joan can really sing soul music, and we all can sort of agree on 10 records we love," Greene said.

Those records range from "classic rock 'n' roll, soul and blues to obscure Nashville soul no one has ever heard of," Greene said.

Gorman said Trigger Hippy's sound, which is "definitely rock 'n' roll, but very soulful, and has a groove to it," aims to get people moving. But their structured, melodic songs are not just jam-band jumping-off points.

"We are very serious about crafting songs," Gorman said.

Trigger Hippy waited until it had songs written before playing for the first time over this past summer in Atlanta. The group might record a few tracks while the members are together on the West Coast, Greene said.

Greene will perform with his own band tonight and Saturday at the Fillmore in San Francisco, then join Trigger Hippy for a Monday show in Petaluma, then the Sacramento show.

"I like to think of myself as a chameleon," Greene said. "When I am sitting in or playing with another band, I have zero ego involved. I just want to fit in and add what I can to the song."

In Trigger Hippy, "everybody is very respectful of each other, and everybody has their own gig," he said. "It is kind of a breath of fresh air for everybody."

TRIGGER HIPPY

When: 7 p.m. Tuesday

Where: Ace of Spades, 1417 R St., Sacramento

Cost: $25

Information: www.aceofspadessac.com, www.triggerhippy.net

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Call The Bee's Carla Meyer, (916) 321-1118.

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