I read another interesting article on SoS last night: https://www.soundonsound.com/people/ken-freeman-birth-string-synthesis.
It provides alternative methods used by Freeman (multiple oscillator banks, multiple points of modulation on the banks etc.) to achieve that lush ensemble sound.
The article also includes an interesting little snippet that concurs with @zebra :
'Much of the perceived richness and warmth of the mid- to late- ‘70s string machines was a consequence of the limited bandwidth of the delay lines used to modulate the waveform, which meant that their high frequencies were suppressed, not accentuated.’
Another thought; as the oscillators were a ‘divide down’ design, I would think deviation from octave to octave would not vary much (as they were using frequency divider chips). However, deviation from note to note (e.g C vs D) could certainly vary depending on each individual notes master oscillator stability and calibration. So perhaps a fixed detune per note could add a subtle effect ‘vintage’ effect as well?
As you can probably tell I’m a fan of the String Synth sounds so I’m looking forward to seeing how this progresses