1. Device, especially in a photoplayer or pipe organ, which permits the operator (or a music roll) to couple and uncouple at will additional pipe ranks or sections of the instrument. Specific couplers are called bass couplers, sub-bass couplers, octave couplers, etc. in pipe organs. 2. Multiplexing device in an orchestrion or band organ which switches groups of tracker bar holes from one group of notes, percussion, etc. to another, providing more musical effects than would otherwise be possible. For example, couplers are used in the Hupfeld Phonoliszt-Violina (to allow for more fingers on each violin), in the Wurlitzer 180 band organ (to increase the notes available in the clarinet, piccolo and trumpet sections), and in the Seeburg KT Special (to provide extra percussion instruments). Details are included in Appendix IV. * Synonym: switch.