This control device is a brilliant concept, making advanced use of available electronic techniques at the time.
Originally the thing is the printed circuit board itself, tightly cased in plastic, so it fitted in the lid of the suitcase
with the actual synthesizer, could be taken out, and connected via a cable to the case.

Since I bought a demonstration-model of the AKS, the circuit board was housed in a hardwood case,
so not fitting in the suitcase-lid anymore. This model is called the Synthi A TKS.
This hardware-situation emphasized the fact, that the keyboard is a seperate device, as a source
of various contol voltages to the synthesizer.

Since the thirty keys at the front of the keyboard are colored black and white, according to a piano,
lots of people complained about the touchpad-construction, because they couldn't play as they liked.
This is caused by the fact that they view the instrument in a 'piano-like' perspective, instead of seeing
the keyboard as just another source of a control voltage, like a pot (a turning knob) or a switch.
This piano-design is handy, if one chooses to tune the keyboard in the classical 12-tone octaves, to make
'common music'. But it stays just one of the millions of different voltage-tunings of the keyboard. . .
The range of the keys from left to right could be inverted, minimized to a half-tone, or expanded to 9 octaves. . .

As soon as I, thanks to Robin Wood of EMS, got hold of the actual circuit diagram of the sequencer-keyboard,
I started adding electronic, so hardware, modifications to it. This process took about 10 years, with many
different stages of options and cases upto the final contraption shown here.

The first thing I disabled, was the exception of the design, being completely wrong imo : the 'Dynamic Voltage'.
Although the circuit itself is very nice, using a small crystal glued to the surface of the board, it was a
kneefall to the 'piano-players' who want to have a 'touch-sensitive' keyboard. The harder, the louder.
In this case, this behaviour becomes rather risky, because 'hammering' on the keys could actually cause
damage to the printed circuit board itself, breaking copper connections, etc.
The only option to realize this option properly, would be to have the actual 30 touch-keys on a seperate board,
with that crystal on it plus its opamp circuitry, connected with a cable to the rest of the circuit.

I decided to use that 'dynamic' line to the Synthi A synthesizer for more useful purposes. Since the cable of the
connection between keyboard and Synthi only provides four lines as separate voltage-control input,
a choice of signal-communication becomes important.

By copying the touch-sensitive circuit of the keys, and using a piece of coppered circuit board, I was able
to add more keys to the hardware-system.
Keys that could activate something with a logic signal, or toggle a flipflop to switch something on and off.

One of my first applications with this, (Caused by the 2nd exception on elegance of the design) was a pad for
'stop the running sequence, but in the proper way'.
Meaning, no immediate stop, but only after properly finishing the whole sequence.
I discovered, that this condition could be easily achieved, by switching on a diode over some capacitor,
active in the 'cycle' department of the circuit.
A lot of of the modifications are done in this way, just by changing components like resistors or capacitors.
Or just cutting a copper-line of the board, then bridge it with a switch again.

Since I build all logic circuitry with the common TTL 74xx series, plus all the leds that were added, it became
inevitable to build an extra power-supply with +12, +5 and -9 Volt for the TKS. As a bonus, this was in favour
of the stability of the power-unit in the suitcase. So I had to adjust the cable-connections.

With the final stage of this instrument, I realized, that I have transformed this keyboard from not only being a
source of control-voltages, but also into a 'logic pulse-processor' and, if one is using a very high clock speed,
as a 'programmable waveform generator'.

Adding circuitry like diode-matrices, logic gates, registers and small memories to the system, appeared to
create extra dimensions to the character of the TKS :
Not only an autonomic 'repeater', but also an autonomic 'player'.

The sequencer of the TKS can control the Synthi 'by itself'. Enabling the start of the read-out is sufficient.
With a running sequence, the TKS provides a second signal, determined by the actual play on the keyboard,
called the 'real-time'-voltage.
So, using two different oscillators, one could generate 'a solo' on top of a repeated pattern.
Now, also this 'real-time' function can control the Synthi 'by itself'. A simple example :

The internal clock of the sequencer-memory can be connected to the trigger-input of the 'random key'.
This means,that with every step of the sequence, another random real-time voltage is generated.
While, at the same time, the 'cycle'-pulse (generated at the end of every sequence) can be connected to the
trigger-input of the Envelope Shaper, as if only in the first step of the whole sequence, a key is pressed.

Not only an autonomic 'player', but also an autonomic 'composer'.
The Synthi is already capable, because of the free feedback-possibilities, to create an unique output, only
repeated every n minutes for example.
I could say : A composition has been generated, according to the composed settings.

Now, this 'feedback' concept is also applied in the logic section. Connections has been made possible.
So the cycle-pulse can be input to a pulse-divider, while output nr 7 of the pulse-divider on its turn controls
the start / stop of the running sequence, In this case the sequence will be played seven times, then stops.
So far, it's a straight start/stop situation of a process, and the output will be the same every time.
But what happens, when the cycle-pulso at the same time is connected to the 'random key' triggering,
providing a certain control voltage to an oscillator, and this oscillator is the actual sequencer-clock ?
The output will not be the same every time the sequence is started, but still it's inside 1 composition, I think.
A matter of variations in performance of the same piece.

How many aspects could be reason enough, to call it 'another composition' ?
Is it enough, if, while the process is running, several conditions could be generated at the
same time, including clock speed  or note-choice, to come out with a total different output the next time ?