selecting audio signals

Hi all,

I'm trying to build an interface for a radio that will allow the user to either speak (by pressing a PTT button) or send a tone generated by the arduino (although i'm hoping to use the AtTiny84 luminet version). So, my question is this...

I want to select either the microphone or the tone pin and connect it to the mic input of the radio. So far i've got a complicated solution using a transistor logic inverter to select either a mosfet allowing the mic to connect to the audio in or a mosfet to provide a path for the tone pin to the audio in. Will this work, and is there an easier (smaller?) solution to this? Also, will i need any sort of op amp etc?

Many thanks in advance!

PS does anyone know the best way to generate a tone with the PWM pin?