I had this idea several years ago and built a version to supply the V- for a quad amp. Al's and Mike's circuits don't work for the reason RonS has illustrated. Cruts' is better but has another problem: when the output of the amp goes above Vin, the base emitter junction will be forward biased and the charge pump cap will again be shorted out. To stop this you put a resistor in series with the base, as RonV has done. The other transistor , PNP in this case , can be replaced with a diode, cathode to amp output. The V- one I built and tested used a diode to charge up the cap when the output was high, and a PNP ( with base resistor ) to transfer charge to the resivoir cap when the output went low. The other sections were only minimally loaded so I don't know how much current this circuit supplied.