[sdiy] lowpass gate etc - the sounds of capacitors

[mikei at marketbridge.ca]

"555" timer with frequency counter approach is good but use a CMOS 555 
timer instead (such as TLC555  TS555  ICM7555) as the CMOS unit 
operates with much smaller leakage currents, giving less error with 
smaller capacitances than the more pedestrian bipolar 555. Have some 1% 
polystyrenes on hand for a calibration check.
Mike