Hi.
You have the Fine Tune knob, on the upper right corner, between the ePaper display and the Phones knob.
Use that to fine tune your synth to whatever other instrument you'll be using with.
Also make sure the OSC's own Fine & Coarse Tune knobs are centered (i.e. at 0).
Analogue synths need a bit of time to warm up once turned on to become stable (that's the nature of analog), so if you don't wait a bit and "tune" it before it warms up, you'll need to retune it again a bit later once the OSCs are more stable.
I don't own a Matrix Brute but the above works for most analog synths that don't have self-calibration (like the MiniBrutes). Hope the above helps
Edit: found a similar post here and according to Dr.Justice (and most likely, the User Manual
), there's an auto tune procedure in MatrixBrute (so now we know).
Please give it a read at
https://forum.arturia.com/index.php?topic=91487.0to run the auto tuning procedure by pressing Panel + Kbd Track [1]