Among the Rocks and Roots make sludgy outsider metal. Not restricted to any one genre, the Richmond duo’s tribal art damage shares the inspirations that compelled Marcel Duchamp to put a urinal in a New York exhibition in 1917. Their hypnotic drone warfare pumps and pulsates with a manic contemptuous glee. It’s a nonlinear, barely musical assessment of time and place born in the moment of creation where sound, intent and physicality take precedent over a carefully selected and practiced sequence of notes. The group celebrates its debut tape, “Samudra Garba Pathe,” on Sunday, April 26, at Strange Matter. Joining it will be the Balinese orchestral sound of Richmond’s Gamelan Raga Kusuma, the shoe-gazing rock of Fat Spirit, Richard Ripper’s noise punishments, the industrial dub of Slow News Day in the Vampire World and the experiments of the avant improvisational collective LRKR from Norfolk. Doors open at 7 p.m. Admission is $8. strangematterrva.com.