When using a hardware tuner, you can ditch the unintuitive tuning instructions in the service manual. In my case that is a Peterson Strobostomp, but any tuner you trust can be used.
Software, Apps, computers: Sometimes software tuners have trouble displaying very low, as well as high, frequencies. Often they are more sensitive to overtones, meaning that they seem to be jumping between semitones. What happens is that they are locking to harmonics, instead of the fundamental, of the currently pressed key. Also the software tuners I’ve used are not showing the same pitch. Maybe it’s a settings issue.
Sources of information
- The Multimoog service manual. That manual was originally written for Micromoog and tuning / trimming instructions are not extended to cover Multimoog’s Osc B. Like many tuning instructions of the time, they’re proposing a complicated procedure that possibly is good if you have an oscilloscope, but not a tuner.
Step-by-Step Instructions
0. If you are serious about this
You should open the Multimoog up and trim the power supply to ±15.00 volts first
Front Panel Preparations, potentiometers
- Tune Knob on the back = Centered
- OSCILLATOR A Interval = 0
- OSCILLATOR A Waveshape = Saw
- MASTER A&B Mix = B
- MASTER A&B Octave = 2′
- OSCILLATOR B Waveshape = Saw
- OSCILLATOR B Doubling = 0
- NOISE = 0
- FILTER Cutoff 10, Emphasis 0
- Modulation wheel: Down (not necessary if you did everything else right, but why not?)
Front Panel Preparations, switches
- Left column: Top to bottom: Off, Single, Off, Off
- KEYBOARD TOUCH Effect switch: Off
- MODULATION Routing: Off
- Right row: Set all of them to the left position*
- Modulation wheel: Down (not necessary if you did everything else right, but why not?)
* Don’t use VCA bypass = ON even though it might seem convenient. The reason is that the pitch you hear when using VCA bypass (without pressing a key) is held by a capacitor which is slowly dropping voltage, so the pitch is going to drop over time. It’s like that with most old mono synths that have a Hold feature.
1. Octave Scale
The idea here is to get the octave interval right before trying to tune the oscillators. MASTER A&B Octave is set to 2′ right?
- Press lowest F. Check the pitch using your tuner. It should be spot on F. If it’s not, make a mental note of how much off.
- Rotate the Octave switch to all the different positions (except Wide)
- Use OSC OCT trimmer on the back of the synth to make the other octaves’ as much off as 2′ is.
2. OSC B
I’m starting with Osc B. Make sure MASTER A&B A/B Mix knob is fully clockwise, towards B
- Set MASTER A&B Octave to 8′
- Press lowest F. Adjust the oscillator to F using OSC B RANGE trimmer
- Press highest C. Adjust the oscillator to C using OSC B SCALE trimmer
- Repeat until both pitches are good.
- Set MASTER A&B Octave to 2′
- Press C4. Be warned, this is not highest C we were using earlier
- Adjust the oscillator to C using OSC B HIGH trimmer
- Start over from the beginning: Set Octave to 8′ and check if Range and Scale are still OK. If not, repeat the steps
3. OSC A
Turn MASTER A&B A/B Mix knob fully counterclockwise, towards A
- Set MASTER A&B Octave to 8′
- Press lowest F. Adjust the oscillator to F using OSC A SCALE* trimmer
- Press highest C. Adjust the oscillator to C using OSC A RANGE* trimmer
- Repeat until both pitches are good.
- Set MASTER A&B Octave to 2′
- Press C4
- Adjust the oscillator to C using OSC A HIGH trimmer
- Start over from the beginning: Set Octave to 8′ and check if Range and Scale are still OK. If not, repeat the steps
* Yes you read it right. It’s the opposite key-trimmer relation to what we used on OSC B
Done
That’s it, you’re good to go