Casio CZ/ VZ/ FZ - Pro Series

Summa: detune them just a bit to create phasing 

--For me, detuning oscillators is one of the most valuable features 
on the CZs. It really livens the sound up and helps to create warmer 
timbres that are somewhat like those of the analogue machines that 
came before them, especially with ring modulation. I've been able to 
create some excellent distorted organ tones and Moog-esque synth 
leads with the CZ. 

Adam