Found this.
Probably the most famous and desirable of all the string synths, the ARP String Ensemble offered a truly luxurious string sound.
Although equipped with 'brass' presets, these were unconvincing and so it was used almost exclusively as a string synthesiser.
In the right circumstances, the ARP String Ensemble could be surprisingly convincing, expecially in the upper registers. However, the 'fizzy' lower octaves tended to highlight the instrument's synthetic origin.
Pre-dating polyphonic synths by some years, the ARP String Ensemble used electronic organ technology to provide a totally polyphonic sawtooth waveform. This was then fed through a simple, two stage envelope shaper labelled CRESCENDO (attack) and SUSTAIN (release) and then onto an analogue 'bucket brigade' chorus unit to produce the 'ensemble' effect.
There were several manufacturers producing string synths that utilised the same basic technique in the mid to late '70s - Elka, Crumar and others - but it was the ARP String Ensemble that offered possibly the smoothest and most convincing string sound of all.
Used by countless performers on similarly countless records, it became a 'classic' sound in its own time (and remains so today). Even the later polyphonic synths such as the Yamaha CS80 and Prophet 5 - which were more than capable of producing rich string timbres - could not quite emulate the rich, chorused texture that was a characteristic of the ARP String Ensemble.
The ARP String Ensemble went on to form the basis of the ARP OMNI which added synth a filter and ADSR envelope and so forth to create a basic 'pseudo-polyphonic' synth. Andrew Gold used one of these to great effect on 'Never Let Her Slip Away'.