The use of a single hole in a tracker bar (or key in a key frame, etc.) to perform multiple functions, usually in combination with other holes. Thus, for example, holes 1, 2, and 3 may have separate functions when used singly; 1 and 2 have a different function when used at the same time; 1 and 3 have still another function, etc. Used in certain of reproducing pianos, large orchestrions, and other instruments to reduce the number of holes needed in the tracker bar (and, consequently, the width of the roll). Examples of multiplexing can be found in the Hupfeld Pan Orchestra, Weber Maesto, and Seeburg KT Special, to cite just three of many examples.