Paging doctor E. Lectronics!
Here's the catch (it was discussed in a thread before, but i can't really blame you for not findinding it, neither can i): there's an extra pin compared to non-mic headphones, which has do to with the microphone (obviously). The thing is there's either no standard for which one that is, or nokia threw it out and did it their way (which is understandable considering the dual nature of the jack). There was a schematic somewhere to show it, but again, i can't seem to find it
Now, it you use a pair of 'phones which has them the other way around, part of the signal going through the buzzers (the ones in your ears) gets routed through the microphone as well. The buzzers are essentially coils, and the mic a capacitor, and this produces an RLC circuit, which oscillates on its own frequency (in this case, around 16-20 khz it would seem). I'm not sure, but i think pressing the call button on the headset disconnects the mic, which removes the C in RLC, making it go silent
Normal 3 pin headphones should all work. IPhone ones will not because they all have the last 2 pins inverted. For all the others, it's hit-and-miss