From Hammond Deggs Music:
Ahh, divider organs, and synthesizers. The origin of "synthesizer polyphony", but often derided for sometimes having a 'thin', or 'static' sound despite providing true "full" polyphony across the entire keyboard range. These organs / synthesizers use a fixed oscillator for a high note, and then use simple divide-by-two flip-flops to get subsequent lower octaves. The upshot of this vs multiple individual oscillators, is that the divider circuit is not only simpler - and cheaper, it doesn't require tuning and is thus more stable overall. The downside of this, is that the divided tones will always be perfectly in tune - and in phase, with their respective top octave. This however can be utilized to advange to get more unique waveforms if desired as we'll explore later.
Divide Down Synthesis Types

For the top most octave to be generated, divider synthesis generally approaches this using two basic methods, each with their own advantages and disadvantages :
Single Top Octave Generator IC Often found in cheaper 'home' organs, string machines (and even the Moog / Realistic MG-1, and Polymoog), these start with a single master oscillator (about 2mhz) running into a single IC that divides this clock by varying integer amounts (/239 for C, /253 for B, /268 for A# etc). This does mean however that everything is tied to a single master clock, and everything (not just the octaves) is phase-locked to each other, which most certainly can yield the 'static' thin sound often attributed to these organs and synthesizers.

These generally do not require tuning as the master oscillator can be crystal controlled, however if they do, they only require only one oscillator to be calibrated / tuned.
This type of sound, if desired can be emulated by this user oscillator.

Adding a second top octave generator / divider set can certainly thicken up the sound much like having a 2 VCO synth vs a single VCO, however this doubles the required circuitry (and cost). The Moog Polymoog is one example...

12 Unique Top Octave Generators This form of divide down synthesis relies on 12 individual unique oscillators providing the uppermost pitch required for the 12 notes. These are still divided down in half for each subsequent octave, however now we have 12 unique sources of pitch for the 12 notes. Aside from providing the possibility to support alternate tunings from equal temperament, this more importantly provides 12 unique and free-running sources of pitch for each note. Thus, chords tend to sound more 'organic' and warm vs their single master oscillator counterparts. And, more importantly, any notes played that use non-octave drawbars / mixtures, will source their sound from a different oscillator, thus yielding a less 'static' timbre to the overall sound.

This has an additional advantage with vibrato: With a single common top octave source, applying the vibrato to this single master oscillator means the sound will vary in pitch perfectly in unison, which certainly adds to the overall 'static' nature of the sound. However, when we have 12 free-running top octave generators and we apply a single vibrato LFO to this, while yes, each note will vary with the LFO at the same phase / frequency, each top octave oscillator will not quite vary at the same amount. This becomes especially important when playing chords or using mixture drawbars - it again adds some more motion and adds to an overall more 'organic' sound.
This type of synthesis is also emulated by this user oscillator, as well as this type of vibrato.

Not all organs used divide down topologies! A few years ago I had an old Conn 640 organ that actually used a unique oscillator for each tone to be generated - 72 of them. This meant there were 72 oscillators (36 tubes) that each required tuning - with a wrench or a socket to a coil no less. That said, it did lend a warmer / more natural sound vs a divider. This is obviously much more complex than a divide-down architecture, and is not emulated with this oscillator.

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