In the Shop with Bob Moog:
A Personal Account, continued

Technical Challenges

The foregoing account probably gives the impression that, other than a few problems, the construction process went rather smoothly and in a rational sequence. Not so. Actually, we frequently switched our work from one keyboard to another, sometimes for reasons of efficiency and sometimes because Moog had not yet worked out certain design details or the solution to some problem. Sometimes we switched just so we could honestly assure each of Moog’s two anxious customers that his keyboard was receiving our undivided attention. This was especially important because, when we began working, the project was already several years behind schedule.

Each step of the way, too, required some experimentation and its attendant failures before we could proceed. For example, our earliest days were spent experimenting with adhesives. We were looking for a type with which we could glue the vinyl ribbon cables to the wooden keys so that the cables could be removed for servicing the keys, then just stuck back down without regluing. After many unsuccessful attempts, we ended up bending and routing the cables so that gluing was largely unnecessary.

Another problem was the clamping of glued surfaces. The keytop sensors, in particular, had to be lined up very precisely with the keys during the gluing process. The clamps we were using at the beginning applied pressure unevenly, causing the keytops to move. Attempts to correct the positioning while the epoxy was drying often resulted in bad glue joints that sometimes were not apparent until after I’d spent hours trimming and filing the keytops to shape. At such times, I tended to sulk, but Moog, ever inventive, rose to the challenge by building jigs that utilized clamps of the type found in industrial mass-production applications, largely solving our problem.

The most serious challenge we encountered was in the installation of a system for sensing aftertouch pressure. Moog had received a license to use a patented system of force-sensitive resistors consisting of a circuit board with a conductive pattern printed on it, loosely overlaid with a resistive film. When no pressure was applied to the film, the resistance between film and conductive pattern was high and no current would flow. When a piece of felt at the bottom of a key would press down on the film, however, the film was supposed to contact the conductive pattern on the circuit board over an area roughly proportional to the amount of force applied, and the current to flow in like proportion. Building this system required a tremendous amount of detailed, intricate wiring and soldering.

Unfortunately, after installing and testing this system in several keyboards, we came to the conclusion that it was highly unreliable for this application. Applying the same amount of pressure would not always yield the same or even a similar amount of current flow, and sudden, unpredictable current spikes were frequent. Moog decided to change the system from one based on resistance to one based on capacitance. He removed the resistive film entirely and covered the circuit boards with a thin Mylar tape to act as the insulating dielectric. The piece of felt at the bottom of each key was replaced with a piece of electrically conductive rubber, to act as the other plate of the capacitor. When the rubber was forced down on the Mylar-covered board, it would expand slightly in surface area and would electrically interact more strongly with the conductive pattern on the circuit board below. This difference would be picked up by the scanning circuitry we installed, and, like the other data being scanned, would be turned into musically usable information. The new system worked like a charm — but now, of course, I had to rip out all the old wiring and replace it with new.

During many of our Saturday-afternoon sessions, Moog and I worked together, he at one workbench and I at another. Over time we arrived at a satisfactory division of labor. Usually he operated the power tools, assisted me with testing, and performed general troubleshooting. I did the operations requiring good hand-eye coordination: soldering, gluing, and shaping of keytops. Occasionally we invaded each other's territory — I on the drill press and he with the soldering gun. Of course, Moog did all the electronics design and provided overall direction for the project; I did all the piano-technician work.

Moog taught me what I needed to know about electronic assembly: how to make good solder joints, how to identify resistor values, and so forth. He also tried a few times to teach me basic electronics, but despite my professed interest in the subject, I proved quite dense (I’d probably breathed in too many solder fumes). Moog did not ask to be taught how to regulate keyboards.
 

Hundreds of electronic components had to be hand-soldered to dozens of circuit boards. Photo Credit: William LaVista

Occasionally our work together was punctuated by other interesting projects. Once Moog took on a short-term consulting job for a company that made stenograph machines for court stenographers, and was researching the feasibility of producing a digital stenograph machine. For a few days, Moog put my key-making talents to use making typewriter keys. On another occasion, in his capacity as a Kurzweil executive, Moog hired me to critique the serviceability by piano technicians of a digital piano Kurzweil was developing. He also kindly took a few days out to read the completed manuscript of The Piano Book and give me valuable feedback.