Suǒ yīn 锁音 (trad. 鎖音)

A category of 9 techniques Ferguson mentions where multiple fingers strike the same string in a specific rhythmic pattern. Unfortunately only 5 are names and explained. By itself, Suo yin is 3 strikes of the same string: Middle finger opening, index finger closing, index finger opening played in the rhythm of 1/16, 1/16, 1/8