The images show the Gibbs phenomenon. You can notice and measure it in all VA synthesizers which use wavetable techniques for waveform generation. You can reproduce it in two difrrenet ways:
1) When you play a very high-pitched sawtooth and zoom into the signal you will see a ripple around nyquist. If you got good ears you can hear 'missing high frequencies' and some notes.
2) When you play a very low-pitched sawtooth you will hear and see ringing on the highest harmonic which sounds like resonance.
It's very complicated math, but here is a detailed article about it:
http://en.wikipedia.org/wiki/Gibbs_phenomenon
Saurus and real analogue synthesizers do not show this behaviour.
Interesting! Yes there are few soft synths that have good sounding waves. Saurus is pretty good here. I love the double saw in particular when the PW control is modulated. Very smooth.
