Rölmo

Rölmo (rol-mo), also known as buk chöl (sbug-chol) or bup chal (sbub-chal), is a Tibetan hemispherical brass cymbals that provide rhythm and structure to the group chants. They look like large knobs with a hole in the centre, through which thin leather handles are strung.
These cymbals are played horizontally by striking their faces together in a tri-part method that includes an initial stroke, an accelerating pulse and a concluding resonating hum.