I've been looking for a solid analog Eurorack VCO for a long time, especially because most Eurorack VCO's do not pitch track very well. I use my Eurorack setup next to digital synths that play chords, so perfect pitch tracking and perfect tuning is very important to me.
This module however has the best tracking I've seen so far in small form factor analog eurorack VCO's!
It also features very extensive calibration options with multiple trimmers if the tuning is off.
The ONA has a very smooth and warm sound with its own character. In my opinion can be somewhat compared to a mix between the smoothness of a Moog VCO and the tightness of a classic Roland VCO.
Next to the traditional waveforms the 2 extra complex waveforms add a lot more tone capabilities. You can find a lot of different sweet spots on these waves by adjusting de PW knob that remind me of classic FM and Wavetable type sounds.
All in all this is the perfect module if you're looking for a smooth Analog VCO for Eurorack with perfect pitch tracking and some additional features up its sleeve.