(I am assuming this to be in the public domain now since the article is over 30 yrs old! A kit was available (see online article pdf). I hope it can be of worth to someone. Also, IC designators have been modified. 2016-09-08, T. Carlyle)

OCTAVIZER

"A new dimension in sound for the hobbyist and musician" by James J. Barbarello.

Connect any electrified or electronic musical instrument to Octa-Vizer and your instrument's single frequency output is expanded threefold. In addition to the single frequency input signal, square waves at fifty-percent of the frequency and one at twenty-five-percent of the frequency are available at OctaVizer's output. All three signals can be mixed in any proportion desired, using the blend and prime controls. The composite output signal can be used immediately, or further processed using filters or other such devices.

The blend control adjusts the relative magnitude of the two square wave signals, while the prime control adjusts the amount of input signal which is fed through to the output. The footswitch operated cancel function disables the square wave outputs when activated.

OctaVizer uses readily available linear and CMOS digital integrated circuits, is powered by a single 9-volt battery, and can be built for less than $15.00.

How It Works. As shown in the schematic diagram, the input signal is AC coupled throuch C1 and C6 to a low pass filter and a level control (R23) respectively. R4 and C2 form the low pass filter with a -3 dB point of about 350 Hz, which filters higher order harmonics that might otherwise be detected in later stages and cause false triggering. The filtered signal is amplified in IC1D along with the DC level set by R2. The output of IC1D is further processed in IC1B where it is squared up and clipped. The output of IC1B is AC coupled through C3 and added to the variable DC level set by R12 in the R11, R12, R13 voltage divider. This composite signal is used to trigger a monostable multivibrator (one shot) formed from IC2, R14, R15 and C4. If pin 4 of IC2 is held low by grounding J2, the output remains low regardless of the input. If J2 is not grounded, pin 4 of IC2 is held high by R16 and the pin 3 output is a pulse train of the same frequency as the input signal.

This pulse train is used to clock two divide-by-2 flip-flops (IC3B and IC3A) which produce square waves at one-half and one-quarter the frequency of the input pulse train. The two flip-flop outputs are attenuated in the two variable voltage dividers formed by R17, R18 and R19. With R19 set at midrange, two equal voltage dividers are formed which attenuate the 9-volt square wave outputs to about 95-millivolts each (a level similar to that of the input signal). As the wiper is moved toward one side, that divider's signal level is decreased while the other's is increased. Therefore, blend control R19 can select either signal alone, or any ratio of the two.

The level of the input signal provided to IC1A is selected by the prime control (R23). This signal, along with the output of the two voltage dividers, is added in unity gain summer IC1A. Since the output of IC1A has a DC component, it is coupled by C5 to output jack J3.

Construction. OctaVizer can be contructed using any standard technique. Standard CMOS handling precautions should be observed when handling IC3. IC sockets may be used if desired. Assemble all components onto the board, being sure to observe polarity for the ICs, D1, and C5. Note that C6 is not mounted on the PC board, but is wired directly between J1 and R23. (Added to PCB. 2016-09-08, T. Carlyle) Interconnect the completed PC board with all jacks and controls. Any suitable case may be used to house the project.

Alignment. If the input to OctaVizer was always a pure, mono-frequency signal, no alignment would be necessary. However, many electrified musical instruments' outputs are generated by a non-linear electromagnetic device (such as a magnetic pickup) and, as such, contain non-sinusoidal  and/or harmonically related components. These components can be detected and cause false triggering. The alignment procedure outlined below will minimize the effects of these components while maximizing the overall responce of the unit.

Begin by setting the wiper of R2 to ground, and the wipers of R12 and R15 to midposition. Connect the input device you will be using, and patch the output to an amplifier. Turn the unit on and rotate the wiper of R12 towards ground until you hear oscillation begin. Now turn the wiper of R12 slightly past the point where the oscillations stop (If a VOM is handy, set the voltage on the wiper to about 3 1/4-volts). Set R23 (prime) to minimum and R19 (blend) to high. As you play the instrument, rotate the wiper of R2 until an output is obtained. If the output is not half the frequency of the input (as determined aurally), back off R12 very slightly. You will notice that when the proper frequency output is obtained, its duration may be short. To increase the duration, adjust R2 slightly in the direction that produces oscillation.

Next, play the highest note you will intend to play. The output will either be correct, very static sounding, or much lower in frequency than anticipated. If the output is correct, no adjustment is required. If the output is static sounding or lower than anticipated, rotate R15 until the proper output is obtained.

The final step is a fine adjustment which will maximize how long the signal lasts while minimizing false triggering. This adjustment consists of alternately adjusting R12 and R2 until you are satisfied you have obtained maximum duration and minimum (if any) false triggering.

Use. OctaVizer can be used over a 3-octave range. As with any new device, it is best to experiment with all controls to determine the effects that can be obtained. A standard guitar can be used with OctaVizer to create a raspy bass guitar effect by setting blend to "Hi" and prime to "Min." An interesting effect is created with blend to midvalue and prime set so both output components are of equal loudness. By striking the strings forcefully, you can create high amplitude hamonics that will false trigger the unit and raise the square wave outputs in frequency by an octave. Thus, by varying your striking force, you can play different octaves.

When viewed on an oscilloscope, the output signal changes shape as shown in the diagram when the blend control is rotated. As you can see, at midsetting of the blend control, a step approximation to a ramp wave is generated. This signal can be filtered to produce a realistic reed-type sound.

A standard foot switch can be used for the cancel control. If not available, one can be made using a push-on, push-off SPST switch and a length of audio cord.

As you familiarize yourself with this new tool, you will find it an interesting and useful specialty effects device.