One of the groovier manifestations of truly spontaneous musical creation is the Buchla Music Easel, introduced in 1973: a modular analog synthesizer, a looping sequencer and a touch-plate keyboard. It was all shoehorned into a suitcase — an on-the-go vehicle by designer Don Buchla to amplify circuitry’s potential for serendipitous inspiration.

On Sunday night at RhizomeDC, Buchla’s brainchild was at the center of a multimedia expression of that in-the-moment ideal, with a performance by the Eternal Now — noise-scene stalwart Marcia Bassett, musician/scholar Ted Gordon and visual artist Jeffrey Perkins.

On the floor of Rhizome’s homey space, Bassett and Gordon each managed a Music Easel, wired into a network of controllers and filters. (Gordon’s array also included a Tocante Thyris, a small, touch-sensitive synth designed by Buchla apprentice Peter Blasser.) The music was, for the most part, more about atmosphere than pulse. Multiple layers of sound were almost always in play, spanning a continuum from abrasive static to sine-wave clarity. The arc evolved from inharmonic drones and swoops to a stretch of rolling, arpeggiated waves reminiscent of musical minimalism, and then back again. Textures hovered in slow-swirling variation before shifting to new ideas; the aural landscape was dotted with gentle surprises of weight and sonic depth.

The visual counterpoint was more directional. Perkins, a veteran of the avant-garde Fluxus movement of the 1960s, channeled a dose of that energy. Projecting slides through spinning, cutout wheels, he gradually shifted from abstract fields of color and shape to an old-school psychedelic anthology of occult, religious and surreal imagery, all in frantically flickering juxtaposition.

Gordon promised a performance of 45 to 80 minutes, but it exceeded even that, extending the negotiations around the concert’s sketched outlines. The music seemed to reach a destination before the images; after some circling, the sounds petered out and Perkins’s projections finished alone. Planned or not, the unbalance was befitting, punctuating an evening that unsettled and sometimes even assaulted the senses. At the same time, the whole experience was also strangely calming. The sonic and visual flux became itself a kind of meditative focus: embracing the analog, organic variability of both sound and existence.