[sdiy] variable capacitor projects?

[rkmoore at memphis.edu]

Hi y'all,

I just got my hands on a very old (I'd guess about 1940's)Philco 
radio/amplifier.  I saw it on the curb for the trash collectors and 
couldn't resist the urge to tinker.  It is sufficiently damaged to make 
it not worth repairing, but there's a slew of interesting old parts.  I 
hope to take the power and output transformers and throw together some 
sort of a 10 or 15 watt guitar amplifier.  

Another part that intrigued me was the large variable capacitor that 
was used in the tuning circuit. I know that variable capacitors are not 
generally used in synth DIY applications because of cost, size, and 
availability, but I would like to use this for something.  Maybe some 
sort of interesting filtering module or instrument preamp could use 
such a capacitor.  Has anyone used one of these in a synth or preamp? 
Any ideas for application?

Thanks,
Richard