Multiple PWM signals from a single audio channel
sounds like you want to use a PPM signal. Instead of modulating the pulse width, you're modulating the time between pulses. 

Say you want to control six servos using a single channel: You'll build a 'packet' with seven pulses, the time between the pulses indicates to the receiver the desired servo position, nominally 1500uS. Let's say we want all six servos to be at dead center. In this case you'll send the seven pulses, each separated by 1500uS. On the receiver end, you'll map each gap between pulses to a servo where you can generate a continuous PWM signal with the desired period and duty. I'll throw up some code if you'd like.