I would like to hook up a variable capacitor to some audio circuits I
built for learning about synths and amps
(schematics are he
http://www.geocities.com/usenet_daug...generators.htm )
http://www.runoffgroove.com/littlegem.html
http://www.runoffgroove.com/ruby.html
http://makezine.com/09/crackerboxamp/
)

because in some of these the capacitors change the pitch, tone or
other qualities.

These circuits run off a 9V battery and use capacitors with ratings
such as
220 uF
100uF,
0.1 uF,
0.01 uF
0.047 uF
so I would want variable caps in this range.
Do these exist? Online all I am seeing is ones rated in pF.

Also, assuming I find these, and get them working in the circuit, and
find a desired setting for a capacitor, how do you measure the
capacitance? I have a multimeter but have really only used it to
measure ohms.

Thanks...