Mad Scientist Jr wrote in
ups.com:

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.


They'd be HUGE. Easily as big as a fridge or a car, even a truck in the
case of 220 µF.

What matters is the timing, as it's timing that matters in amps and
synthesizers, except for power supplies or sample and hold circuits where
capacity is more important.

To get long timing with small capacitors, use large value resistors, and
make sure you have low leakage capacitors.