Percussion X: Instrumentation is left at the discretion of the performers. However, the following rules apply: Each performer (A, B and C) have a set of the same instrument with undefined pitches classified as H (high) M (mid) L (low). Each performer also has another instrument, different from the above mentionned HML set, referred to as X. HML sets of the performers A, B and C may be (and should be) different from each other. This can also be achieved by tuning and/or modifying each set so it sounds different from the other performers' Instruments with fast and precise attacks as well as rapid decay times are to be preffered.