4/23 Wurlitzer Console
Size – Theatre organs are commonly described by two pieces of information: Size and Manufacturer. Size is indicated by two things: Number of Manuals, and Number of Ranks. For example, a 3 keyboard Wurlitzer brand organ with 16 sets of pipes would be called a “3/16 Wurlitzer”. A “4/23 Robert Morton” is a Robert Morton brand organ with 4 manuals (keyboards) and 23 ranks of pipes.
Organ specification - An organ designer “specifies” the various ranks to be included in an instrument, and at what pitches (16’, 8’, 4’, etc.). He/she also “specifies” where the pitches of the ranks are to be available on the various manuals and pedalboard, and the ordering of all the stop tabs and controls on the organ console.
Opus # -- Opus usually refers to the sequential numbering of musical compositions. In Theatre Pipe Organ terminology, it is the serial number of the instrument. The Wurlitzer company, for example, assigned a sequential Opus # to each instrument it built as it left the factory.
Style -- Wurlitzer terminology referring to the Model of the instrument.
Wiring Schedule – Wurlitzer terminology referring to the wiring configuration of the instrument.
Blower Number – Serial number of the blower (the electric air turbine powering the instrument).