SAN FRANCISCO--It's safe to say that John Butler is a student of the KISS principle.

That would be "keep it simple, stupid," not the one that involves menacing face paint and music that is decidedly less so.

In the John Butler Trio's set at the Fillmore last night, the Aussie roots-rock songwriter's lyrics leaned heavily on progressive slogans and simple metaphors, often taking a backseat to the grooves. That said, the group showed that uncompromised musicianship and heart is enough to force even the most devout hippie haters to push up their lighters.

This was no jam band noodlefest, where songs are forsaken for circuitous solos over meandering rhythms. Butler was economical with his solos, keeping them brief and interesting, while bassist Shannon Birchall and percussionist Michael Barker were outstanding, stretching and bending the rhythm in creative way.

The beginning and end of the night was buoyed by the sublime presence of acclaimed guitarist Kaki King, who served as opening act and joined the group for part of its encore.

In her set, King used loop pedals to lay down multiple guitar parts, as well as fret tapping and slap bass techniques to create a complex, lush sound. She even jumped on a drum kit for a few tracks to really fill out the sound.

One had to continually check the stage to make sure it was just her up there. King even packed a bit of humor into her repertoire, dryly ribbing a crowd that was clearly distracted by cocktails and conversation by saying, "Can you turn up the chatter in my monitor because I'm not getting any. Thanks."

Butler and company took the stage to the sound of Nina Simone's "Feelin' Good," a good sign if there ever was one. They launched into "Pickapart," a brawny, bluesy groove that emphasized Butler's slide acoustic guitar playing.

Butler has a unique vocal delivery that tends to emphasize the rhythm of the vocals over the content. Most of the songs featured him singing in a rapid-fire, half-rapping delivery--think a folksier Anthony Keidis. Plenty of songs focused on progressive causes, from the pro-environment "Treat Yo Mama" to the police state concerns of "Oldman."

But it was the night's love songs that saw Butler break into song, straying from the hasty delivery in favor of soul, particularly on the crowd favorite "Peaches & Cream." Following a beautiful and nuanced guitar intro by Butler and King, the track anchored the encore and was as syrupy sweet as its title suggests, with Butler leading the crowd through repeated chants of its chorus: "All I know is all I know is I love you, yes I love you."

But lest a bed-in break out, the group closed the night with the perky "Better Than" and "Funky Tonight," the two singles off Grand National, the group's latest album. Both tracks put the musicianship back at the forefront, and showed that Butler does indeed have songwriting chops. They're just occasionally hidden behind grooves that tend to incite fans to break into the "Sugar Magnolia" dance.