component selection - How to select a proper transistor?

I've got a schematic that calls for an unspecified "NPN Negistor". From my understanding of the circuit, the NPN is an oscillator that generates two audio tones for testing. Here's the schematic:

I've got a drawer full of about a dozen flavors of NPNs, how on earth do I choose which one to use with such sketchy information?

Answer

That's an interesting circuit...

I can find references of BC547 and 2N2222 being used as negistors. This might be a "try it and see if it works" sort of situation.