Prog Organ -  A Virtual Pipe Organ System

Much interest has been expressed in the digital organ system used as the basis for the article Re-creating Vanished Organs, and described in more detail in Digital Organs using Off-The-Shelf Technology.  

The system as a whole is known as Prog Organ, standing for Programmable Organ because it can simulate a wide variety of instruments.  The sounds of the organ are stored in SoundFonts and consequently they can be played in the usual way, but limited to only one stop at a time, from any MIDI keyboard connected to a PC with a suitable sound card.  However, to enable more than one stop to be combined at once and to simulate different manual departments, couplers, etc, a special-purpose control program is required in addition.  This program is the heart of the Prog Organ system.  The program interfaces a standard organ keydesk to a Windows IBM PC fitted with one or more SoundFont-compatible sound cards, enabling it to be played in exactly the same way as a pipe organ.  In particular, stops are used (and behave!) in the normal manner, which is not always the case with other systems.

A blind capture-combination system is incorporated within the control program as a simple alternative to needing expensive fully motorised stop keys or draw stops at the keydesk - all the user needs to do is to provide the necessary pistons, plus an optional lamp or LED to indicate at the keydesk that a blind combination is in use.  As mentioned above, the sounds of the organ are contained in SoundFonts, a standard and widely used synthesiser format which enables the user to substitute sounds of his/her own or to adjust the voicing of the instrument.  Virtually any number of "organs" can be simulated from a single keydesk, the desired one being selected by choosing which of several configuration files is to be read by the control program.  These are straightforward script files written in plain text which can be modified by the user, or completely different ones can be created.  The files perform functions such as informing the control program where each stop can be found within the SoundFonts, which physical stop key or draw stop at the keydesk corresponds to it, etc.  Input from the keydesk passes to the PC in one of two ways: either via a fairly simple interface to the parallel port of the computer, or MIDI inputs can be used in the usual way.  The parallel port input option is unique to Prog Organ and not offered by other systems, and it provides the cheapest method of interfacing a PC to a keydesk for those with basic electronic constructional skills.