When an organ person speaks of something being an organ, they are not
talking about a console and chamber and pipes.  To an organ person
there is a Swell Organ, a Great Organ, a Pedal Organ.  Technically
these divisions are all separate organs, playable from a different
manual of the console.  Only in the theater organ did one room of pipes
become available on every manual on the console.

In the day of the Welte Philharmonic, the Echo Organ was merely a
division of the organ like the Swell, Great, Choir, Accompaniment, and
Solo divisions.  While the console uses Great, Swell, and Choir, the
roll uses Accompaniment and Solo manuals.  These two may exist only in
the Philharmonic relay.  The Echo is most often played from the Great
manual and must have a stop tab that says "Echo on Great."  There will
also be a "Great Manual Off" tab, which allows the Echo to play by
itself or with the Great.  If the Echo is available on other manuals it
is what we call a "floating" division.

The Echo was a standard part of larger Kimball organs and Weltes, and
especially Kimball-Weltes.  The Echo on every Kimball I have serviced
used basically the same stops.  There would be a Vox Angelica, Viola
Ætheria, Nachthorn, Forest Flute, and Vox Humana.  Perhaps others have
more ranks but the ones I have been inside of all contained these
stops.  The Viola Ætheria was the celeste with the Vox Angelica, which
is the straight-tuned string stop.  The Nachthorn is the 4-foot octave
of the 8-foot flute.

The Echo division is the softest division on the organ.  In residential
installations it is most often found on the stair landing or across the
room from the tone chutes from the main organ.

Yes, you could play duo organ pieces using the Echo Organ, but it would
be from the same console, using the pistons to turn the Echo on and
Great off, and back and forth.  There is not normally a second console,
as you may have perceived by now.

The Welte roll uses the Echo division with, I believe, all stops on
together.  The flues have a tremolo and the Vox has a tremolo as well.
I think the roll turns on the Vox separately with tremolo only, never
without.  The main chest of flues has a tremolo turned on separately 
from the roll.  The roll also uses a 61-note metal harp; the harp is
not in the Echo, but I thought it is unusual these days and should be
mentioned.

D.L. Bullock
www.dougbullock.ws