[sdiy] A different approach to frequency shifting?

[Thomas Hudson]

I came across an article in CSound Magazine from Summer 2000 about an approach to frequency shifting I hadn't seen before. It uses a quadrature oscillator and two multipliers followed by two LP filters and then another quadrature oscillator and pair of multipliers. The difference in frequency between the two oscillators determines the shift:

http://www.csounds.com/ezine/summer2000/processing/index.html

It seems that this method would be simplest for thru-zero effects. The article is in the context of a digital implementation, but has anyone used this technique in the analog world?

TH