Old school additive synthesis only used sine waves to add harmonics. I’ve not dug deep, but I have read people mention both “wavetables” and “additive” when discussing the Chord machine. If it’s pure sine waves, then the brightness will be limited by processor power and interface real-estate. If it’s wavetables or SCWFs as the oscillator sources for the addictive process, I guess there’s a chance Elektron can add noisier waveforms.
(I don’t own an ST. I’m just wasting time when I should be working and day-dreaming a bit)