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Micor Coupland Digital Synthesizer

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The Coupland Digital Music Synthesizer is a 16-voice polyphonic real-time instrument with a full 88 key keyboard. It began developed in the 1973 but never released commercially. Said to be one of the first digital synthesizers. The Coupland was designed for the performer to use the frequency domain specification of the musical voice harmonics to model sounds that would be controlled by an ADSR function.

The instrument was based on a waveform buffer model that is now a widespread practice. The idea that was independently conceived by Moore and Coupland. The sound engine was driven with high precision phase generator, of which only the high order bits addressed the buffer. According to Dave Hamma, the synthesizer had a very unique interface that required the user to enter a mathematical function to define the wave form. While complex, this low-level approach allows the user to enter any wave form they can think of by entering the formula for it. Additionally, a logarithmic algorithm could be used to apply audio level and ADSR amplitude modulation to the signal generated for each voice. This avoided the cost and heat dissipation of available commercial multiplier modules.

The synthesizer was quite powerful, utilizing what is known today as additive synthesis. With 12 wave table generators, the oscillators could be programmed with up to 256 harmonics. For control of the sounds, there were two envelopes, for pitch and for amplitude modulation of the oscillators. The system also had an LFO for vibrato and tremolo effects. For physical control, the Coupland's 88 key keyboard was said to be velocity sensitive, with multiple pedals for foot control, but the real feature was the synthesizer interface that looked like a console right off of Star Trek that was said to be touch controlled as well.

Technical Specifications
Type: Digital
Synthesis: Additive
Oscillators: 2
Waveforms: Additive
Osc Modulation: Envelope, Keyboard, Knob, LFO, Oscillator, Pedal, Sequencer, Velocity
Oscillator Notes:
+ 12 wave forms
+ 256 fourier harmonics per oscillator
+ variable phase angle
Envelopes: 2
Envelope Notes::
+ 5 stage envelopes
LFO: 1
Polyphony & Tuning
Polyphony: 16
Timbrality: 2
Tuning: Standard
Modes: Polyphonic, Split
Storage: Internal
+ 20 sequences
Chips and Operating System
+ Based on MSI TTL logic
+ TI-990 * TI-9900 minicomputer chips
Case: Keyboard
Keyboard: 88 keys
Controls: Velocity, Buttons, Knobs, Sliders, Pedal - Control, Sequencer
Display Type: LED
Audio Output Connections: 1/4" Phone Jack
DAC Bits: 12
Year Released: 1973
Year Discontinued: 1979
Units Made: 5
Design Notes:

Designed by Rick Coupland and John Moore.

The idea was first conceived and the basic concepts invented in 1973 by Rick Coupland and John Moore, old friends and systems programmers who were working at Ramada Inns Micor division (Phoenix, AZ) at the time. The project lasted from 1973 until 1979, included two product version, but never reached commercial success due to inadequate funding.

In 1975, Coupland left Micor to work full-time on creating the instrument, building the first, and 8-bit version. Micor subsequently funded the project and a team including a consulting professor of music and consulting physicist, along with the usual engineers. They designed and built a prototype of the 12-bit version.

Due to funding constraints, the prototype was rushed to a showing at the [1] conference where the fragile, wire-wrapped prototype failed to function, leading to significant embarrassment. However, the concept and design was solidly proven, and with continued funding would have been a commercial instrument representing a significant improvement in the state of the art.

A Texas Instruments TI-990 minicomputer performed the non-real-time Fast Fourier transform processing necessary to convert from the frequency domain specification to the time domain waveform buffer format. It also handled user interaction such as specifying sound parameters. The second version used a TMS-9900 microprocessor for the same functions

The first version used only 8 bit precision for its output digital-to-analog conversion (DAC). The instrument suffered from aliasing, which was not due to the typical cause of too low a sample rate or inadequate post-D/A filtering. Rather, it was an inherent effect of low precision calculations in the digital circuitry - round-off error produced digital non-linearity and extra harmonics resulting in digital mixing with the sample rate. The problem was solved by dithering, which did not noticeably affect the intended output, but through the natural characteristics of human hearing caused the narrow-band high frequency alias to become imperceptible. In general, in-depth study of psychoacoustics was used to solve such problems and provide some technical constraints.

The 12 bit instrument was more advanced than the 8 bit prototype, and was enclosed in a stylishly modern plastic case with a futuristic touch-sensitive console above the keyboard. It was small and light enough to be a practical performance instrument. It is still in Coupland's possession.

Notes from John Moore on their work:

I worked with my old friend Rick Coupland on the Coupland Digital Synthesizer, especially the conceptualizing in 1973 and 1974 (while we were designing and bilding the infrastructure of the Ramada Inns/Micor hotel reservations system). We independently invented the waveform buffer, a technique to maintain very accurate frequency by having only the most significant bits of the phase counter address the buffer, and a sneaky multiplication circuit that used a weird logarithmic representation ( I think it was log base square-root of 8) for applying the attack/decay/sustain/release to each output channel. This trick was to avoid the very expensive and heat generating multiplier modules on the market at the time.

The original synthesizer used only 8 bit output, but was 16-voice real-time polyphonic and had an 88 key keyboard. We discovered an aliasing effect that was not due to the sample rate or A/D post filtering, and determined it was caused simply by the quantization effects while still in the digital logic (this is an odd concept that needs more explanation than I can give here). We applied dithering of the master clock to make it go away without noticeably affecting otherwise affecting the sound.

The project then gained funding from Micor and was expanded to include modern packaging and a touch sensitive keyboard. It was changed to 12 bit (better IC's were available by then), and the team included a professor of music from UofA.

It was rushed to the trade show (a marketing decision resisted by the technical people), poor Rick was hyped in the marketing literature (against his wishes), and the subsequent difficulties in keeping it working were embarrassing. Both versions used all MSI TTL logic and lots of wire-wrapped prototype boards, which is why it failed at the show.

The second version had a stylish production packaging and a futuristic touch-sensitive console above the force sensing keyboard. Internally was a Texas Instruments 990 mini (or perhaps, by then, the 9900 IC - don't remember) which provided the user interface and did the non-real-time FFT's required to transform from the harmonic-spectrum based voice construction into the time domain waveform buffer. The prototype was shown to several top popular musicians, who were very impressed and wanted to buy the units, but it never made it to production. Rick still has the original prototype. I believe that original 8 bit prototype was given to University of Arizona, where it's fate remains unknown.

Comments on the Couland from Dave Hamara

I've seen the Coupland called vaporware enough times that I figured I should set the record straight. While the slick looking, performance oriented unit pictured in Vail's book may never have made it past the brochure stage, there were several working prototypes built, and I had the privilege of spending 3 months in a 16-track studio with one of them.

In the Fall of 1980, I was poking my nose into some dim and dusty corners of the music building at the University of Arizona in Tucson when I came across what was obviously a computer with a keyboard attached. Being an EE major with a CSC minor playing keyboards in a band by night, I immediately went to the department head and asked if I could play with it. I was told that the professor who had brought it to the University had left, taking with him all knowledge about the unit. They said that if I could get it to work I could have 6 hours / week in the studio with it for the rest of the semester.

The unit consisted of a card cage with 8 or 9 wire-wrapped cards (one with a TI-9900 processor on it), a dual 8" floppy, 25x80 CRT "dumb" terminal, an 88 key pressure sensitive keyboard, a stack of unlabeled floppy disks, and a one page xeroxed "instruction sheet". Amazingly enough, when I plugged it all together and turned it on, the floppy drive read light came on, so I started feeding it the disks from the pile until I found one that booted to a command menu. After a couple of very late nights it was actually making sounds.

The control software on those disks must have been in a very early state, because it was nothing at all like the brochure \:\) The voice and the modulation waveforms were entered as mathematical functions of the form "sin(x)+cos(2*x)/2+sin(4*x)/4". You could get a square wave with round((sin(x)+1)/2), and with the mod function you could create sawtooth waves. There was no "filter" block, and no way (that I ever discovered) to use the ADSR to control any aspect of the voice besides amplitude.

Those limitations aside, though, it was a truly amazing synth for its day.

At the risk of being too long winded, I'll pass on a little history as well. One evening I took a girl I was dating into the studio. She saw the Coupland and told me that her father had showed her one just like it. It turned out that her father worked for Micor, knew Rick Coupland, and knew quite a bit of the history of the unit. He told me that there were 5 working prototypes: one at Arizona State University in Phoenix, the one I was working on, one that Rick had kept, and he didn't know what happened to the other two.

He also told me that Rick was very bitter over Micor pulling the funding for the project just as it was nearing completion. He said that when they pulled the funding, Rick quit Micor and took every shred of project documentation with him. Micor sued to get the documentation back, but Rick said that he had destroyed it, and no one could prove otherwise.

I asked if he could arrange for me to meet Rick, and he called a couple weeks later to say that Rick was not interested in talking to anyone about the project. Period.

I hope this sheds a little light into another dusty corner of electronic music history.
MSRP List Price: $20,000 - $30,000 - convert
References & Sources

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