Keyboard not in tune

I just got the synth kit and am having fun with it. It can make some fantastic spacey sounds. However, the keyboard bit is not quite in tune. When I set up a simple Power>keyboard>oscillator>speaker and play the octave notes, the high note is about 1/2 step flat. I guess it’s not sending quite the correct voltage across the octave. I realize that this is not really meant to be a serious music synthesizer, but it would be nice to at least play in tune on the keyboard.

Any suggestions?

I have this problem too. I’m going to try using one of my Arduino bits as a USB MIDI input to see if it’s actually a problem with the Keyboard bit or a problem with the Oscillator. I noticed that in some octaves it is more ‘in tune’ than others (though the intonation is still bad across the keys) so it probably is just an inaccurate Keyboard… which is good, because the Keyboard is not an ideal way of playing anyway!

USB Midi Input for Arduino project:

Same for me and I have two keyboards with identical problems.

Isn’t the tuning knob on the oscillator designed to help you get the keyboard in tune?

The problem isn’t that the oscillator is out of tune with another instrument. It’s that the intonation of the keyboard is off so that the octave is about 1/2 step flat.

I see… hmmm.

Hey All!

I just wanted you to know that I’ve reached out to our engineers about this issue, hope to have a response soon. Thanks so much for your patience!

I have the same problem but do not think that the keyboard is the issue.
I have measured the output voltage from the keyboard and found that there are almost perfect volttage steps between the keys, 0,165 V between full step tones and 0,083 V between half steps checked over two octaves.

So the problem is maybee in the oscillators.

Now I have checked the oscillators.
They need a raise between 0,162 V and 0,181 V for stepping up one full note but the difference between two keys on the keyboard is equal 0,165 V checked over two octaves.
So the keyboard is OK but not the oscillators. I have four with the same problem.

yes, the oscillators are out-of-tune when using midi too. Odd that Korg didn’t check this. Is there a workaround?

Hello All!

It sounds like the oscillators in question are out of tune.

There are simple instructions for tuning the oscillator in the Synth Kit manual on page 21, but below I will post more detailed instructions:

power -> keyboard -> oscillator -> speaker (set to a LOW volume)


  1. Set octave thumbwheel on the keyboard to one of the middle octaves
  2. Push the lowest button on the keyboard and listen to the speaker. Remember the pitch.
  3. Push the highest button on the keyboard and listen to the speaker. This “should” be one octave above the pitch in step 2.
    4A. If step 3 is too high, then turn the tuning thumbwheel on the oscillator counter-clockwise until it is closer to being in tune.
    4B. If step 3 is too low, then turn the tuning thumbwheel on the oscillator clockwise until it is closer to being in tune.
  4. You must now repeat steps 2 through 4 until the interval between the two notes is a perfect octave. This can take several iterations.

If you cannot remember the pitches, the I recommend that you use a guitar tuner. There are several free guitar tuner apps for android.
If you are using a tuner, then you should be able to get the octaves to be in tune within 10 or 20 cents, which is pretty good.
The system is analog, so there are imperfections. Tuning will be best in the middle of the oscillator range, and in the middle octaves of the keyboard.
If you change ranges, you may want to retune, but usually this will be a minor adjustment.
Operating at high volumes, or with a low battery will make tuning more difficult.


Thanks for that detailed instruction, Patrick. I will try it with a guitar tuner. I may have discovered it by accident by playing around with both tuning knobs on the oscillator, as I have not noticed the poor intonation as much as I did when I first got the synth kit. When I first noticed it, I had the oscillator course tuning set to a pretty high pitch.

Can you explain a little more what the thumb wheel on the oscillator is doing? I thought it was just a fine tune and the knob was a course tune.

@davidtberg I can’t say for sure yet but it definitely seems related to how the oscillators map the input voltages to the output pitch. After tuning it “close enough” to any note of your choice (A or C in my case), if you jump to different octaves the pitches won’t sound as you’d expect.

In fact, if you play it alongside an Arduino-based oscillator you’ll definitely notice the dissonance after jumping far from the pitch you used for tuning. The difference is small and can be corrected by turning slowly the small ‘tune’ knob, though, so I guess it can be called a ‘feature’ of the oscillators.

We always had problems like this with the original synth’s
. And after they warmed up, we had to tune them again. A constant issue, but the sounds we could generate were wonderful and def worth the work.

This doesn’t seem to be related to “warming up” oscillators though. These oscillators do not go octave to octave reliably under ANY circumstances. I think its a flaw. I’ve tried putting some trial and error adjustments into an arduino sketch to keep them closer, but as synth oscillator tuning goes, well, these are actually really bad in that respect - no other term for it. I hope Korg enhances them or 3rd parties offer better options here.

I totally agree with oldlibmike.
We need a better oscillator.

Mmm caffeine.

A good source of power and connections with shoes makes a difference in the audio.

Since we are also dealing with analog it’s not perfect like a digital signal. Unlike analog which is effected by a lot of different variables including real world variables we have no control over. We are tuning with digital devices which allows us to see and hear the frequency. We can fine tune the signals using our phones. 100 years ago it was a pair of ears and a tuning fork.

Try to fine tune with a guitar tuner to a close enough approximation and then close your eyes to finish the tuning. This is where creativity comes into play.

This looks like a limitation in the occilator but we only have so much control over analog inputs and outputs. That’s why analog creates character or a unique timber. This is the strength of analog because our bits will never have exactly the same because timber. Like most analog instruments

Think about it.

Why don’t all guitar brands sound exactly the same?

Why does my monotron have to warm up longer in Colorado than in Texas?

Why doesn’t my Korg filter sound exactly the same as my moog filter?

Why does a record sound warm and CD quality perfect?

How many licks does it take to get to the tootsie roll center of a tootsie pop?

If you want absolute perfect go digital. Digital Software sounds the same on all PCs. Analog is not perfect just like people… unique.


Yo @sc4r4b!

I am also active on a photography forum which has a large contingent of film photographers, and the discussions sound very similar to this.

No surprise Chris! The two artistic mediums of light and sound are intertwined by the same physics.

Do you use an analog or digital camera? Film or memory card? :stuck_out_tongue_winking_eye:

I’m actually a professional product photographer. Except I’m so digital that my job title is 3D artist. See what I did there?

Hey scarab, I’ve used both digital and ana… film. (It’s not analog, it’s film, which deals with discrete particles of silver, not an infinitely variable silver density.)

Everyone realizes that digital has better resolution than film, it has better range, and you can edit it much easier to a much greater extent. On the other hand film offers the option of throwing your image into the soup and being amazed at what comes out. It’s pure alchemy.

Once upon a time, back when I was a little bit, I too worked as a camera for hire. It was real fun, and possibly the most difficult job I have ever had.