To John Wale, Jody and all,

> From: Mr J D Wale <essfc@csv.warwick.ac.uk>
>
> Subject: MIDI Program Changes
>
> There has recently been discussion in the MMD of MIDI-operated
> mechanical organs. Thinking through the way MIDI changes sound patches,
> how would one correlate MIDI program change messages to organ stop
> settings ?

I am the owner of Octet Design Corp, and the engineer in charge of the
design of our MIDI interface for organs, the UM1. The UM1 is a relay
driver as well as a console encoder and stop knobs encoder, which in
most cases operates in conjunction with a PC. We are faced with the
problem you mentioned and are designing software to take care of the
program changes.

The UM1 encodes key presses and stop knob changes as MIDI note
messages, one MIDI channel per manual, one or more channels for stops.
Usually, a single MIDI wire is sufficient to route this information to
the PC. The PC can optionally record this stream with a sequencer
software, and edit it and play it back later.  The UM1 is also a relay
driver, receiving MIDI note messages and driving its outputs
accordingly. Usually one MIDI channel per rank, one or more channels
for stop relays (if they exist). Large organs require multiple MIDI
output ports to reduce delays.

The software we're doing will insert itself before the PC's MIDI
outputs; it will receive MIDI messages from the console or the
sequencer and route them to the outputs. The note messages that
correspond to stops are translated into multiple note messages to drive
the appropriate pipes. This translation "table" is programmed by the
user with a friendly windows interface. Several tables can be stored on
disk for different combinations. A stop can cause any note or range of
notes from any manual(s) to drive multiple notes on multiple ranks,
with transposition. Mapping is available for percussion instruments. A
stop can also cause a program change message and a MIDI program change
can be interpreted as a stop. Stop changes can also drive stop relays.
Combination changes can drive multiple stop relays (the UM1 has a MIDI
sysex message that can change all its outputs simultaneously,
eliminating the delay in this case).

We would like to hear any comments, questions or wishes concerning the
features of this software so we can make a product that satisfies most
demands.

Laurent Coray.