[sdiy] VCO circuits using the 555 timer?

[David Betz]

I bought a few 7555 and 7556 chips recently and would like to  
experiment with building a VCO. I got the idea for using the 555 from  
the fact that they use it in the PAiA FatMan but I've been unable to  
find any other VCO circuits that use the 555. Can someone point me to  
some examples of using it to build a VCO? My first idea was to  
duplicate the VCO part of the FatMan circuit but I'm not sure I  
really understand how they are using the 555 in that circuit. It  
doesn't match any of the examples I've seen for how to use the 555 in  
astable mode. For example, the timing capacitor is wired differently  
than the example circuits I've found. Can anyone point me to  
resources of using a 555 for musical applications?

Thanks!
David