In the mid-70s synthesizer designers started looking into a new market - guitar synthesis. The idea was that a guitar could be used to control a synthesizer via circuits that converted pitches to control voltages. As there were many more guitarists than there were keyboard players and synthesizers offered so many new sounds, the motivation was that this could be a lucrative market to move into.
The first guitar synthesizer I can find was the "Polyphonic Guitar Synthesizer" created by Bob Easton of 360 Systems and he followed up with the Slavedriver and Spectre. A few years later in 1977, Roland released their GR-500 / GS-500 combination and Korg followed with their X-911 Guitar Synthesizer in 1979.
ARP also ventured into this market and their story is particularly interesting because it was brave and innovative, but ultimately attempted before the technology available was able to handle their ambitions and it sadly came at a price for the legendary company.
The project had three main parts, with the Avatar being the only product that saw the light of day. The other two parts were a huge six-voice polysynth that would have both a guitar version and a keyboard version. The guitar version was dubbed the "Centaur VI".
Thanks to the help of the Alan R Pearlman Foundation I had the pleasure of interviewing David Friend and Bill Singer of ARP who worked on the Avatar project for my documentary "Electromotive - The Story of ARP Instruments". Found at 1:17:19 in the embedded link below is the specific section of the film where we cover this bit of musical history.
Please take a moment to check out the Foundation here: https://alanrpearlmanfoundation.org
One of the engineers who worked on the Centaur VI passed on what he could recall about its features.
Two oscillators per voice with each oscillator generating four footages (like an organ) that could be combined to create square waves or sawtooth waves.
ARP's 4-pole filters.
Two ADSR envelopes and an envelope follower.
The far left panel could be interchanged for the guitar or keyboard interface for the planned polysynth.
Above: David Friend working on the Centaur VI and Bill Singer ready to play it from his guitar. These photos were taken by ARP's then VP of Marketing Worldwide, Bob Hoffman, at Pete Townshend's studio during a demonstration of the Centaur and Avatar. They are reproduced here with permission.
As discussed in "Electromotive...", the Centaur VI just wasn't viable as a product due to the sheer amount of components required to build it and their associated cost. The estimates were that it would have had to have been sold for around $15,000 per unit and that's around $64,000 when adjusted for inflation, so it's not difficult to understand why ARP abandoned that part of the project having made only one prototype.
As the Avatar was already up and running and priced at $3,000 (around $12,700 now), ARP continued on and released it.
Here's some photos of Bill and David demonstrating the Avatar with some famous faces from the same session as the Centaur.
The Avatar starts with a proprietory hexaphonic pickup that connects to your guitar. This pickup was designed by Ron Hogue and is six pickups in one pickup, which is crucial to the Avatar sound and functionality.
There were two sizes of this pickup, .44 for Fender guitars of the era that have a very wide string spacing and .41 for Gibsons and other guitars with more standard spacing. I've scanned the pickup installation procedure and it can be found below.
The cable is very unusual and is a Lemo S-Connector at one end and 6-pin Din at the other. This carries the six individual string signals into the Avatar in isolation.
There is a setup procedure to calibrate the Avatar to your guitar and the manual and original instructional cassette can be found here.
ARP Avatar Instructional Cassette
with Bill Singer
ARP Avatar Guitar Synthesizer
ARP Avatar Hexaphonic Guitar Pickup Installation Procedure
What does it do?
The first thing you get is the Hex Preamp sound, which comes out in stereo with three strings left and three strings right. There is an additional mono output and also two main outputs, so this signal comes out in several places. There is a main output on/off switch on the panel and this can be toggled with a footswitch on the front too. This turns off the main output, but not the individual outs.
You then have a second option which is Hex Fuzz or "clean fuzz". This is a fuzz circuit for each individual string signal and with no cross talk and a stereo split, it's a very distinctive sound.
The Hex signal can also be selected in the audio mixer signal of the synthesizer as a "special effect", the other being pink noise. The audio mixer runs into the voltage controlled low pass filter, manual high pass filter and amp. Using the envelope follower and the ability to trigger the synths' onboard envelopes, the Hex signal can be processed by the filter whilst the cutoff is modulated. This signal is in mono, but it can be combined with the direct stereo Hex signal too.
Next we have the synthesizer! This is a two oscillator analogue monosynth that is very closely related to the ARP Odyssey, but with some key differences. Using the string select switches, you can choose which strings the synth should read from and then play it from the guitar monophonically.
The fundamental problem with the technology of the time was that it couldn't do the pitch extraction very quickly and so there was not only a lag, but a variable lag depending upon the pitch of the note you were playing. On the low E string it averages 40ms, 20ms in the next octave, 10ms in the next and 5ms right at the top of the guitar range. As the Hex signal has no delay and each section has its own out, the workaround is to monitor the Hex and then budge the synth audio as best you can after recording. Not ideal, but at least a solution.
The next issue is that you have to adjust your playing to avoid unwanted notes or harmonics being accidentally picked up. The same issue is present with the Hex pickup sounds where every click and clack and (supposedly) muted string audibly comes through if you're not careful. The problem of the sensitivity six pickups in one!
In terms of interacting with the synth from the guitar, pedal and footswitches there are some options available. The frequency of VCO 2 can be modulated from the envelope follower (normal or inverted) or the foot pedal. These same options are also available for control of the VCF frequency. As there's a ring modulator and oscillator sync, many different complex timbres are available through these functions.
The sample and hold can be triggered from the guitar and is a modulation source for both oscillators and the filter. It's worth noting that the Avatar gives up the S&H Mixer modulation option of the Odyssey to accommodate the envelope follower and this removes the ability to cross modulate VCO 2 with VCO 1, itself or the noise, which is a slight shame.
The footswitches can switch the portamento on and off and latch the synth so that it sustains until the switch is pressed again.
Finally, the Avatar has an external audio input that runs through the filter.
Here's a video demonstrating everything I've explained above!
How does the conversion work?
Here's a description of how the Avatar converts pitch to CV that Nathan @ Synthchaser kindly helped me with.
In a nutshell, we count the number of cycles of a very fast clock during each cycle of an incoming note, which measures the period of the note. The number of clock cycles counted is transferred into a digital memory location or "register".
The value in the register is used to divide down a second clock and this creates a square wave that can be converted from a frequency to a control voltage which in turn, is directed to the synths oscillators to sound a note that matches the one you played on your guitar.
The wave shape created by a guitar is too complex to be used directly, which is why the conversion to a square wave is necessary.
How many were made?
Various sources claim there were only 300 Avatars made, but I've become a little skeptical of this. There were five Avatar models - 2220 - 2225 and mine is a model 2223 with serial 1014. I've since seen model 2223 serial 0714 and another in the 600s.
These may be batch 07 number 14 and batch 10 number 14, but combined with the other models (2220, 2221 etc) and the fact that they regularly come up for sale, it seems very unlikely that there were only 300. There were 520 Linn LM-1 models and around 500 Oberheim TVS models and those are nearly impossible to find, so that also seems contrary to the 300 Avatar figure. It's quite possible there were more like 1,000+ Avatars, but I guess we'll never know for sure.