Archive of the former Yahoo!Groups mailing list: MOTM

I've heard that it is difficult for a VCO to create a sine waveform
(or really a good quality sine wave). Is this true and why is it
so? Its obvious to me that it would be harder to generate a sine
wave in comparison to a square wave, but what is specifically
challenging theoretically and in practice?

Some people complain about the purity of sine waves generated from
VCOs.. does this matter to you? Do you find sine waves useful in
subtractive synthesis or could you do without this waveform?