One of the big drawbacks of the Bionic Sax and Trumpet (Polyphonys, Vol. 3, nos. 2 and 3) is the selection of octaves. In my prototypes, I just used a rotary switch. But this proved extremely difficult to control with any amount of finesse, so I took away the switch, added an IC and a few calculator-type switches, and came up with the circuit below.

The circuit replaces the octave selector in the previous sax and trumpet schematic. The clock is fed in from the oscillator/tuning circuit and the output goes to the input of the top-octave generator.

On the Bionic Sax, the three switches are mounted in a vertical line on the back of the body and are operated with the left thumb. I included a thumb rest alongside the center switch. On the trumpet, experiment to find the point that is easiest to reach and mount the switches there.

Now, when you use the instrument, it will play in a moderate-to-low octave with no octave keys depressed. To get the next lowest octave, press the lower two keys simultaneously (and a well-placed thumb can hold both down if the keys are mounted close together). Pressing the bottom key along gives the lowest octave. Higher octaves involve the upper two switches. For the octave above the "normal octave", hit the center switch. Pressing both the top and center switches simultaneously gives the next highest octave, and pressing the top switch alone gives the top octave.

After getting used to the configuration, this octave controller works well and sure beats the heck out of a rotary switch. If anyone has an alternative idea for controlling octaves, let me know in care of Polyphony.