"That was just so you know I'm not a robot," quipped Merrill Garbus after fumbling the intro to a song at Johnny Brenda's on Friday night. There's nothing robotic about Garbus' onstage presence - the bug-eyed, almost feral expressions she made as she sang were evidence enough of that - but the precision with which she assembled elaborate rhythm tracks out of overlapping vocal and drum samples made her seem at least slightly more than human.

Garbus, who records under the name Tune-Yards (or, as she prefers, tUnE-yArDs), was joined on stage by a bassist and a two-person saxophone section, but the most critical interaction was the one between her right foot and the pedals clustered around her microphone stand.

Beating time on her hip with a drumstick, she acted as the conductor of her own personal orchestra, using the pedals to record snatches of song and stray drum hits that magically coalesced in perfect unison.

On "Gangsta," from her second album, w h o k i l l, she began by mimicking the sound of a police siren, adding the distorted thump of a bass drum and the off-beat click of a drumstick on her microphone stand. Her voice took on the gravelly patois of a Jamaican rude boy as she sang, "What's a girl to do if she'll never be a Rasta?"

On "Bizness," Garbus played a staccato melody on a ukulele, evoking the clipped sound of a West African thumb piano. She was steeped in the region's music during years spent in Kenya, and has acknowledged the influence - "Any African music it sounds like I'm stealing, I'm stealing," she told one interviewer - but her one-woman approach shields her from any risk of copying her source material too closely. On "Hatari," she sang in Swahili, but the song's hectic overreach seemed to emanate from a country wholly her own.

Garbus' tourmates Buke and Gass, who joined her for the herky-jerk of "Es-So," share her handmade approach.

Named for their modified instruments (a baritone ukulele and a guitar-bass hybrid), Arone Dyer and Aron Sanchez shifted direction with each song, and often several times within them. They were hectic and uncontained, and sometimes simply a mess, but Dyer's lyrical voice provided enough ballast to keep them from capsizing completely.