Freeman string symphonizer
The Freeman String Symphonizer was a 5 octave synthesizer of the 1970s. (The first prototype being shown prior to 1970, but the most well known shown in 1970, the second according to the Sound on Sound article) It was finally manufactured by the Chicago Musical Instrument Co. and was also known as the Cordovox CSS. Its sound was related to that of the Arp String Ensemble - cool glassy sounding strings. Eventually Ken Freeman tried to strike a deal with the company Ling but they abandoned their interest in it. Lowry a division of CMI finally struck a deal after some deliberation.
The delay in getting the Freeman to market caused it to be purchased by a limited number of people. Some of them were fairly famous people but its release was overshadowed by both the Eminent Solina and Crumar Stringman, both of which cost less to make due to having only one oscillator largely.
The Freeman had 25 oscillators. One was used to control a 'top octave synthesizer' chip (the common MK50240 in later versions, M087 or SAA1004 in earlier ones. A TOS is a digital chip that generates a 'top octave' of notes from one high audio frequency input signal). Thus creating a stable note spacing that has digital perfection. The other 24 oscillators have 2 assigned to create each note so that there are a total of 3 possible pitches for each note. Each slightly different to create that wonderful analog warmth as the tones of 2 out of 3 gradually drift a tiny amount to give a dynamic beat frequency between them. Much like real instruments gradually change in pitch every so slightly due to temperature changes.
After the creation of these high octave notes, frequency divider chips are used to create the lower octaves for each 'rank'. So there are three complete sets of tones that can be mixed to create more or less overtones in the sound as one rank is tuned an octave below the other from the beginning. The 'High' and 'Low' buttons on the front select which group is selected or they can both be mixed for a thicker octave overtone on each note. The 'low' must be on to hear anything on the highest octave since they did not provide enough frequency divisions to layer the two across the whole 61 key keyboard.
Due to the fact that all tones are present all the time for use, it had no restrictions on how many notes could be played at once, unlike most synthesizers at the time, which were often monophonic. (Aside from the duophonic ARP Odyssey of the day for instance.)
The Ensemble effect invokes the TOS rank to add the additional thickness to the other two 'ranks' of oscillations. But the two that have 1 discrete oscillator per note have an 'animation amount' slider associated with them. 6 low frequency oscillators are grouped to notes such that it maximizes the effect for typical chords. In other words, makes it always sound like there are as many different vibrato rates as possible to again simulate an actual symphony. Further a built in spring reverb helps simulate a hall environment. And again one could choose 'cello' (16'), and 'violin' (8') tones.
There was a 'touch' (delayed) vibrato setting, and a 'glide' switch on the foot volume pedal (found also on many Lowery home organs), which dropped the pitch one-half step. This made it unique compared to other string machines that had only one oscillator and relied on delay line chips to produce the ensemble effect (chips that have to reduce the audio bandwidth to mask the digital clocking).
It was a heavy machine - about 70 lbs - and was rather durable except for the removable keyboard cover which looked like it hinged up, but rather pulled straight out.
It was used by The Who, Jan Hammer, Chick Corea, Elton John, Ramsey Lewis, Peter Sinfield, Peter Bardens of Camel
Recently, it has been emulated in software by GForce, with their Virtual String Machine software.
References
- Ken Freeman & The Birth Of String Synthesis, Sound On Sound, February 2007