Drop a filter into the chain and the bright raw oscillator turns warm. Sweep the cutoff by hand and hear how subtractive synthesis was born.
The sawtooth wave is bright and buzzy - too harsh on its own. A filter sculpts the tone by cutting out frequencies.
We are using a low-pass filter: everything below the cutoff passes through, everything above gets quieter. Turn the cutoff knob down and the sound gets warmer and darker. This is the heart of subtractive synthesis.
Drop the filter into the chain: VCO SAW -> Filter IN, then Filter LP -> VCA IN (the VCA input was empty since we removed the direct VCO cable).