Let's see...
"Key of Middle C" on a piano...
On Sheet Music...
On a Piano...
Note it's not A3 ....
It's approximately ~262 Hz (Cycles per Second)
Cyan color key is C4 (Or middle C)
Go here for help on this
https://en.wikipedia.org/wiki/C_(musical_note)
Note the Amber - color key, A4 - is 440Hz.
Ok, why the above music lesson?
Most Vocals don't use much above 2kHz - 2,000 Hz - unless you want to make your voice sound like scratching fingernails on a chalkboard...
Let the "overtones" take care of themselves, you just have to keep your voice in the correct pass band.
So, A3 to about A5 (if you're a "tenor") Bass? Try A2 to A4 .
So
@kaos513 - If you can use both tones - simultaneously - please do so, just remember to run the attenuator to keep their Fundamentals - 1.4kHz, 2.8kHz and above - out - from skewing your tuning results.