Violin technique once. "Double stopping" is also used to mean playing on three or all four strings at once, although such practices are more properly called "triple" or "quadruple stopping". Collectively, double, triple and quadruple stopping is called "multiple stopping". However, triple or quadruple stopping is more commonly just called a chord. Sounding an open string alongside a fingered note is another way to get a harmony. While sometimes also called a double stop, it is more properly called a drone, as the drone note (the open string) may be sustained for a passage of different notes played on the adjacent string.
Quadruple product Quadruple product In mathematics, the quadruple product is a product of four vectors in three-dimensional Euclidean space. The name "quadruple product" is used for two different products, the scalar-valued scalar quadruple product and the vector-valued vector quadruple product or vector product of four vectors . The scalar quadruple product is defined as the dot product of two cross products: where a, b, c, d are vectors in three-dimensional Euclidean space. It can be evaluated using the identity: or using the determinant: The vector quadruple product is defined as the cross product of two cross products: where a, b, c, d