[sdiy] What is a quadrature oscillator good for?

[eq927 at freenet.carleton.ca]

Grant and list,
Quadrature oscillator makes a nice modulation source to provide vibrato 
for two VCO's - "fuller" sounding than simply modulating both VCO's from 
one phase. Invert the two outputs and you get a 4-phase LFO suitable for 
modulating four parallel BBD delays, or four PW circuits, or four 
sawtooth shifters. Put two VCA's  after the sine and cos outputs and the 
additional inverter-derived outputs get level control for free, for 
global level control of all four outputs.
Regards, Mike