Both the original Minimoog and the Midi Mini have three oscillators and a reference oscillator producing the standard 440Hz tuning tone.
If you need to tune the instrument, the best advice would be to ditch the internal reference as a long term standard of correct pitch because this might drift, or be adjusted incorrectly.
Instead it is better to use a modern tuning checker and set the VCO tuning directly, or you could tune up the internal reference and use it to reset the VCO tuning during the session because it shouldn't drift over a short period.
For the rear panel adjustments, use a screwdriver with an insulated handle.
Tuning Oscillator 1
- Turn on the Power switch (On = Up) and allow the instrument to warm up for ten minutes before making adjustments.
- Set the controls as shown in Fig. 2 and make sure the Pitch Bend wheel is in the centre position.
- Switch on the A-440 reference tone.
- Switch on the Oscillator 3 Mixer switch. Adjust the Oscillator 3 Frequency control to create a perfect unison with the reference tone.
- Switch off the A-440 reference tone.
- With Oscillator 3 on and now tuned to A-440, switch on Oscillator 1. Press and hold high A and tune for near zero beating with Oscillator 3 (two octaves below) by adjusting Range 1 on the rear panel. Fine tune for perfect zero beating with the front panel Tune control.
- Release high A and depress and hold low A. Adjust Scale 1 on the rear panel for perfect zero beating with Oscillator 3 (one octave above).
- Return to high A and observe that adjusting Scale 1 has a slight effect on the range. Repeat steps 6 and 7 until perfect zero beating is obtained at both low and high A.
Tuning the Oscillator Range Switch
With Oscillator 1 on, high A pressed and zero beating with Oscillator 3 (440Hz), switch the Oscillator 1 Range control on the front panel to the 32' foot position and adjust the Octave control on the rear panel for perfect zero beat tuning.
Tuning the Remaining Oscillators
- Return the Oscillator 1 Range switch to the 4' position.
- Turn off Oscillator 3 using the Mixer switch.
- Turn on Oscillator 1 and Oscillator 2.
- Depress high A and hold. Adjust Range 2 on the rear panel for near unison with Oscillator 1. Adjust Oscillator 2 front panel Frequency control for perfect unison.
- Release high A. Depress and hold low A. Adjust Scale 2 on the rear panel for perfect unison. Repeat steps 4 and 5 until perfect unison is attained at low and high A.
- Switch off Oscillator 2. Switch on Oscillator 3 and click up the Osc-3 Control switch on the front panel.
- Set the front panel Oscillator 3 Frequency control to zero.
- Press high A and hold. Adjust Range 3 on rear panel for near unison with Oscillator 1. Adjust Oscillator 3 front panel Frequency control for perfect unison.
- Release high A and press and hold low A. Adjust Scale 3 on rear panel for perfect unison. Repeat steps 8 and 9 until perfect unison is attained at low and high A.
- Take a break!
Why don't we get to have this much fun with modern instruments?