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.