(thus adding an octave below unison pitch and one or two octaves above), and supplying the necessary relays and wiring, the builder of an electrified (often, more precisely, electropneumatic) organ could multiply the tonal resources of the instrument severalfold without adding more ranks of pipes. Mutation stops such as the octave fifth (at an interval of a twelfth) and the superoctave third (seventeenth) could be derived from the same rank with equal facility. A single 97-pipe extended rank, playable at each of four pitches on each of three manuals and at three pitches on the pedal, would thus be represented on the console by no fewer than fifteen stop tabs. Herein lies the secret of the “mighty” Wurlitzer. A Unit Orchestra with six ranks (diapason, flute, string, trumpet, vox humana, clarinet) might have more stops at the console than a traditional concert instrument of one hundred ranks. Hope-Jones’s contributions to organ design were not limited to ingenious wiring schemes. He held numerous patents for innovations and improvements in various phases of organ design. He invented the familiar tongue-shaped stop tablets, the horseshoe-shaped stop rail, and double-touch (adding more assertive stops when a given key is depressed more deeply than usual), all of which became standard features of Wurlitzer and other theatre organs produced in the U.S. and abroad during the silent film era. He is also credited with inventing or developing several voices, including some that are unique to theatre-organ sound, such as the tibia clausa, a large-scaled stopped flute typically played with extreme tremolo; the diaphone, a powerful bass stop with a moving valve-like resonator in the mouth of each pipe; and close imitations of several orchestral instruments. Other features characteristic of the theatre organ in which Hope-Jones played a pioneering role were the installation of various sets of pipes in separate recesses below or adjacent to the stage, thus achieving a primitive stereophonic effect; the placement of all divisions under expression, that is, enclosing all pipes in sound-tight boxes (often built of concrete) with pedal-controlled shutters, permitting wide variations in loudness; richer and deeper tremolo effects than were customary in church or concert instruments; high-powered centrifugal blowers capable of providing adequate wind for pipes voiced at 10 or more inches of water; tuned percussions such as marimba, xylophone, harp, glockenspiel, and cathedral chimes; bass, kettle, and snare drums, gongs, tambourine, castanets, and cymbals; “toy counter” effects for use