As with guitars the oscillators of the Synvoiz will change their tuning from day-to-day. It should become a habit to tune them before you start working. When I made my first steps into modular synthesizers with a Doepfer A-100 I never cared about tuning the oscillators and wondered later how strange it sounded combined with other harmonic elements in a mix. If you already learned a musical instrument you should be aware of this topic – I never had that pleasure.
The good news is: beside the loosing of the tuning after one day the relation between the two oscillators stays the same. So when you once set them right, you just need to turn the mastertune knob to get back where you were. But one step after another.
Depending of the surrounding setup in your studio you need some kind of reference. This could be an outboard measurement gear like a guitar tuner, a frequency generator/counter or, if you go directly into your DAW with the Synvoiz, a plugin. No matter what you use don’t hesitate to compare the tools. There are several free plugins available on the internet. I like GTune by Graham Yeadon. For Mac this might be another good one. Although they all bypass the audio it should be noted that the one from Waves isn’t bit accurate which means the plugin introduce strange quantization noise.
Mind that you probably have to change your current patch if you go out to your tuner from the audio out. Filter settings with high resonance will interfere with your attempts to tune the synth. Also some tuners like the plugin from Waves have trouble with sinus like sound sources.
Beside the normal audio output of the unit you can use the square wave output (SQ). By doing so you exclude any further pitfalls.
I would tune the second oscillator by ear depending of what amount of phasing between them you like. No need for reservation – with all the prerouted amplitude and frequency modulation and syncing options many interesting sounds build up on a “wrong” tuned second osc. Experiment!
When you change the octave range of your midi notes it is worth to check the tuning again. You will find out that not every note is in the right pitch. Welcome to the analog world!