Hello Apollo Collectors -- As there seems to be an increased interest
lately in the early Melville Clark pianos and it appears that a few
more Solo Apollo pianos have turned up in varying states of preservation,
I thought I would provide an update on the system in my Automatic Solo
Apollo, S/N 9754, which I have been slowly restoring for far longer
than I ever anticipated.

I have now made enough progress in the restoration to be able to relate
how the system is supposed to operate, although I am not yet finished
and I am not yet able to fill in all the blanks.

Additionally, it is widely known that Melville Clark was quite the
innovator and experimenter, with the result that there is a lot of
variation between pianos he produced; so features that apply to my
specific piano may not be present in others.  This will be a very long
posting, but I believe it to be the most complete posting yet written
anywhere on the topic of Melville Clark Solo Apollo pianos.

It appears that there are at least two different "formats" of Solo
Apollo: the "AUTOMATIC" and what, for lack of a known original term,
I will call "CONVENTIONAL".  My piano has the lowest serial number of
any Solo Apollo yet discovered to the best of my knowledge and is one
of perhaps two known with the AUTOMATIC expression features.  I am not
certain of the details of the possible second.

A few basic commonalties amongst all known Solo Apollo pianos:

The tracker bar is 132 or 134 holes, 9/inch hole spacing, for 15-1/4"
wide roll.  There is no automatic tracking device.  Powered by a
spring wound roll-drive motor.  Has a switch block that will plug the
SOLO ports by means of a lever and allow ordinary 88-note rolls to be
played.  Has a "main" stack with 88-notes played by pushing down on the
keys with horizontally-mounted striking pneumatics in the same manner
as nearly every Melville Clark player.

The Solo Apollo piano also has a second "Solo" stack of 55 pneumatics
that play those 55 notes nearest the center of the piano action.  By
keeping this Solo stack pneumatically isolated from the main stack it
was intended that the music could be separated into "SOLO" and "ACCOMP"
(factory terms) and each part of the music could be simultaneously
played at different vacuum intensities.

What is not (yet) known is exactly how all of these pneumatics are
actuated.  88 Main + 55 Solo = 143 striking pneumatics, which exceeds
the quantity of tracker bar holes.  Presumably some of the notes must
be tubed with Y connections to allow two notes to strike from one hole,
but further research on other pianos will have be conducted to sort
this out.  Allowing that some of the tracker bar holes are used for
expression coding -- at least in AUTOMATIC pianos -- this leaves a
still greater discrepancy.

My piano is not much help in resolving this since -- for reasons
I do not yet fully understand, although my piano has 55 pneumatics
in the Solo Stack, complete with valves -- 19 of the solo pneumatics
were permanently disabled by the factory and have _never_ been used.
Even the ports for the nipples leading to them were plugged and sealed
under the original finish on the stack.  This leaves me with 36
operational Solo pneumatics: 88 Main + 36 Solo = 124 striking
pneumatics.  Subtracted from the 134 tracker bar holes, this leaves
10 holes for expression, which coincides with what I have been able
to figure out from the remaining tubing.

I speculate that "AUTOMATIC" Solo pianos have the extra Solo pneumatics
disabled to make their tracker bar holes available for expression
coding, but I cannot confirm this without seeing another "AUTOMATIC"
piano.  I question why all of those additional parts were added to
"AUTOMATIC" pianos and then disabled.  One would think it would be
easier to simply leave them all out, if they were not ever going to be
used.

There are three different varieties of "Solo" stacks currently known,
all differing substantially in their method of construction, but
presumably functionally identical.  I will arbitrarily assign numbers
1, 2, and 3 to these different stacks.

Type 1 Solo stack is screwed directly to the back of the main stack,
so both stacks are inserted and removed from the piano together.
However, the Solo stack is a separate bolt-on component that can be
disassembled as a unit from the main stack after removal from the
piano.  The striking pneumatics are arranged vertically with the hinge
facing downward.  "L" shaped wooden fingers on pivots (located at the
junction of the "L") are connected at the top of the "L" by a rod to
the striking pneumatic lift up on the piano action stickers by means
of small feet added to the piano action for this purpose.  The Solo
striking pneumatics are smaller than the main striking pneumatics and
open significantly wider.  (A completely gutted piano, or even a stray
upright action, could be identified as having once been a Solo Apollo
by the presence of these feet as there are only 55 of them.)

Type 2: Solo stack is screwed directly to the back of the main stack,
so both stacks are inserted and removed from the piano together.  The
striking pneumatics are arranged horizontally and look very much like
an inverted copy of the main stack pneumatics.  I do not know if they
are dimensionally the same as the main stack pneumatics.  They push up
on the piano action much nearer the top of the stickers and eliminate
the need for all of the extra "L" pivot pieces.

Type 3: Solo stack is a completely separate unit, mounted under the key
board.  I am not sure of the orientation of the striking pneumatics,
but they are presumably mounted horizontally.  Piano action is operated
by wooden buttons that stick up through the key frame from below.  I am
not sure exactly where they mate up with the piano action.

"CONVENTIONAL" Solo Apollos seem to all be foot-impelled.  The foot
pump has three large supply ports.  Two of the supply ports provide
vacuum to the main stack at the bass and treble ends.  On my piano the
stack is not internally divided, but it has the two supply ports.  The
third supply port is connected to the Solo stack.  A lever mounted on
the left side of the piano under the keyboard is connected to a
shutter/choke that is built into the reservoir on the left side of the
foot pump unit.

By sliding this lever back and forth you can vary the amount of vacuum
allowed into the Solo stack in infinitely variable steps between Full
Open and Closed (my terms).  This allows the intensity of the Solo
stack to be varied somewhat independently of your foot pumping.  The
main stack intensity is controlled by your feet.  Quite likely it is
rather cumbersome and difficult to make this setup operate with any
consistency.

"AUTOMATIC" Solo Apollos have the same foot impelled system as
described above.  In addition they also have an electric pump and
a system of expression pneumatics.  The expression is controlled
automatically by means of two pairs of ratcheting pneumatics that
control the intensity in Three steps.  One pair operates the main
stack vacuum supply; the other operates the Solo vacuum supply. These
expression pneumatics can also be operated manually by means of buttons
in a small drawer that slides out from under the keyboard.  There are
five buttons, labeled in order: "Solo Loud, Solo Soft, Accomp. Loud,
Accomp. Soft, Crash".  There are three more buttons, unlabeled, and not
mounted in the drawer which control Bass and Treble Hammer Lift and
Sustain.

On the left side of the spoolbox is a switch labeled "AUTOMATIC" with
positions for Off and On.  This controls a switch block with 12 ports
and allows the expression tubing to be blocked off entirely while still
in "Solo" mode.  This is also important when playing 88-note rolls as
will be described later.

There are two pneumatics to control Shut-off: one stops the spring
motor and the other pulls the electric power switch to stop the pump.
I am not clear on how this is supposed to operate in practice.
Without vacuum you cannot pull the spring motor lever to off (this is
a substantial pneumatic) but turning off the electric power shuts off
the pump.  There is no mechanism present on any Solo Apollo I have seen
to accommodate a REWIND function.

At present the interchangeability of the Solo rolls with and without
AUTOMATIC is unknown, but I now suspect they are NOT interchangeable.
If the "CONVENTIONAL" Solo tracker bar uses all of the holes to play
music (as I theorize may be necessary to play all 55 Solo pneumatics)
then that format of piano would interpret all of the expression coding
from the "AUTOMATIC" rolls as music notes and sound terrible.

Conversely, if the Solo rolls without "AUTOMATIC" have music notes
in locations interpreted as expression coding by an "AUTOMATIC" piano,
then either those music notes would be "played" as expression, or, if
the expression were shut off, those notes would simply be dropped from
the arrangement entirely.  Obviously, neither option would sound good.
Further documentation of "CONVENTIONAL" Solo pianos will be necessary
to confirm or rule-out this supposition.

I have been attempting to decipher the tracker bar layout and tubing
for my piano as this is not completely documented anywhere that I am
aware of.  My piano has a number of missing and broken original tubes,
which means that tracing the original tubing was not completely
possible.  Unfortunately the tubing that was missing was largely that
at the extreme ends of the tracker bar/spoolbox, which corresponds with
the expression holes.

To further complicate matters every tube controlling an Automatic
function is routed from the tracker bar to a switch block that shifts
between Solo Apollo and 88-note playing modes, routed to another switch
block which allows the Automatic features to be disabled independently
(I presume this was to allow non expression-coded rolls to be played
with transposition, see below), routed to another block that makes
a 90-degree turn and then the tubes are routed to either a valve block
or to expression pneumatics with valves built in.  Many of these links
in the chain were missing, which makes reverse-engineering rather
difficult.

And, if that were not bewildering enough, it has now become apparent
that, in addition to the Solo Apollo format and regular 88-note rolls,
this piano is also intended to play some format of 11-1/4" expression
roll, which brings up even more confusion over tubing.  I have assumed
that the most likely format candidate for a Melville Clark expression
piano to play in the 1909-1911 time frame in 11-1/4" size would be the
Apollo Red X rolls.  Using that tracker bar scale for the Apollo X
format on page 98 in "Treasures of Mechanical Music" by Reblitz and
Bowers, in conjunction with remnants of surviving tubing, I have been
able to decipher some of the tracker bar scale in greater detail.  Can
anyone confirm that the Apollo X expression system was in production
in this period?

The presence of the "AUTOMATIC" off/on function allows the 11-1/4"
expression rolls to be played, but also permits the expression ports
to be disabled and allow ordinary 88 note rolls to be played with the
ability to _transpose_.

Below is what I have found.  I have some comments and questions about
this, which I will reserve until after I finish this listing.  Note
that the multi-format capability and the need to accommodate rolls of
varying widths with different functions in different places means that
some of the same hole positions in the tracker bar have 2 functions,
depending on how the switch blocks are set.  First I will describe the
switch block in SOLO mode:

#1: Sustain (??)
#2: Solo Soft Expression
#3: Solo Loud Expression
#4: Accomp Soft Expression
#5: Accomp Loud Expression
#6 to #23: Solo Stack notes 1 to 18
#24 & #25: ??CRASH?? (Surviving tubing seemed to indicate
    use for expression coding, but this is not at all clear.)
#26 to #111: Main stack notes 3 to 88
#112 to #129: Solo Stack notes 19 to 36
#130: Expression ??Hammer rail Bass??
#131: Expression ??Hammer rail Treble??
#132: Shutoff
#133: Expression ???
#134: Sustain???

Some additional observations on this tracker bar layout:

Surviving original tubing indicated Hole #1 was tubed to Sustain.
However, in every single "AUTOMATIC SOLO" roll I have run through the
piano (more than a dozen so far), Hole #1 is _never_ open.  Hole #134
is frequently open and uses long chained perforations that look like
sustain function.  The original tubing to this hole was missing, so
cannot confirm.

However, in my collection of rolls I have one special oddball roll
which is a 15-1/4" wide QRS "88 NOTE" roll.  Although the leader says
"For Use on Solo Apollo", this roll has NO perforations corresponding
to the Solo stack.  It does however have all of the expression coding
and it is the only roll I have yet found that uses Hole #1.  The
perforations in that position also look like the chain perforations
used with Sustain and, for the majority of the time (but not always),
are an exact mirror of the perforations over hole #134 throughout the
arrangement.

Does this coding make sense to anyone?  What sort of Sustain function
would be used with tandem perforations like this?

Holes #1 and #134 are the usual width for 9/inch tracker bars, but are
both .210" (5.4mm) tall.  I do not know the reason for this.

Every "AUTOMATIC SOLO" roll thus tried has the following instruction
printed on the leader:

"1st - Try music at Test-Slots to insure proper tracking using extreme
small apertures only."

"2nd - Advance roll past Test-Slots."

"3rd" - Adjust Tempo lever and turn on power."

The test slots, when centered, line up with holes #2 and #133.  As both
of these holes correspond to expression holes, I do not understand how
these would allow you to "try music" as described in the instructions.
I am also very unclear as to the precise meaning of "extreme small
apertures only".  Does anyone have any ideas on this?

Once past the test slots, there are a series of perforations that would
be used to ratchet [to step] the Solo and Accomp expression intensities
down to their lowest setting before the music begins.

On every "AUTOMATIC SOLO" roll thus far, there is a perforation in the
roll at hole #130 that opens and closes just before the music begins.
This hole is used throughout the music, and then it has consistently
been the LAST hole to open after the music has ended but before the
Shutoff function is activated.  I do not know the function of this
hole.  Does this describe any logical function within the context of
an expression pneumatic system?

I should also note here that I have more than a dozen varieties of
rolls that all say "Solo Apollo" or "Solo Art Apollo" in various styles
of label with or without "AUTOMATIC".  All of the "Solo Art Apollo"
rolls thus far examined have expression coding, but do not say
"AUTOMATIC" on the labels.  None of the rolls that say "Solo Apollo"
without "AUTOMATIC" on the label have any expression coding.  As yet
though I do not know the differences between all of the different label
styles.  I also have "TEMPOSET" and "TEMPOGRAPH" rolls as well, that
indicate "SOLO" somewhere on the label.

All of the rolls, regardless of specific format listed on the label,
were made by QRS.  Does anyone in MMD-land have access to QRS Catalogs
from the 1908ish to 1918ish time frame that could take a look and see
if any or all of these different types of rolls are defined in the
catalogs?  I think that QRS catalogs from this time period would be
an invaluable tool for discovering more details about these different
formats and I would imagine that they are described in at least
a cursory fashion to prevent purchasers from buying the wrong format
if they are all in fact incompatible as I suspect.  I would be very
appreciative of any scans or copies of catalog pages that address these
roll formats.

The tracker bar layout is quite different when the switch block is
thrown to "88" mode and is as follows:

#1 to #19: All plugged
#20: Crash
#21: Sustain
#22: Expression Soft
#23: Expression Loud
#24 to #111: Main stack notes 1 to 88
#112: Hammer rail lift (Bass?)
#113: Hammer rail lift (Treble?)
#114: Expression function??
#115: Expression function??
#116 to #134: All plugged

Positions #21, #112, and #113 in the tracker bar each have an extra
hole above and below the straight line of holes in the tracker bar.
This allows the middle hole (in a vertical orientation) to be used for
a SOLO note, but for expression in the 88 note mode.  The top and
bottom holes are common through the switch block, so this means that
the Sustain and Hammer Rail Lift functions will operate slightly before
the music note(s) is/are played and will be held until slightly after
the music note(s) is/are ended.

Note that, unlike the listed scale for the Apollo X rolls, notes #1 and
#2 in the piano are not disabled.  However, those notes correspond with
"Rewind" and "Shutoff" so would not be played as part of the music in
any roll arranged for the Apollo X system.

Holes #114 and #115 correspond to "ACCENT" and "PLAY" per the
information in "Treasures of Mechanical Music."  I do not know the
meaning of those functions.  Could someone please describe to me what
is happening pneumatically when the "ACCENT" and "PLAY" functions are
activated in the Apollo X system?  Knowledge of these features may
help me resolve the purpose of some components whose precise function
is unknown at present.

This is by no means a complete or definitive description of the Solo
Apollo system and further research may indicate that some of what
I have determined thus far is incorrect.  However, I thought it
worthwhile to share what I have found and hopefully other people out
there will find even more information to add.

Thank you to anyone that may have something to add to this.

Troy Taylor - In surprisingly sunny, but not very warm,
Edmonds, Washington