Finally, Dave is beginning to give us the complete story.

Now, Are you thinking of generating audio tones using the pic in order
to transmit AFSK, audio frequency shift keying? This will basically be
filtered and sent to the microphone input of a transmitter. Or are you
going to use the pic to control a tone generator? What you use as a
transmitter has a lot to do with how complex the PIC program will be an
which PIC you will use.

Several years ago my company hired an engineer to develop a fax/modem
phone line switch using a 16 bit PIC. I don't remember the number.
Anyway, the circuit he designed and the software the programmer
developed watched for the phone ring tones and for the tones sent by
fax machines. It also generated the ring tones to ring the telephone on
the line it had selected. Just as with your project, it never had to do
all at the same time, although,I think the timer generating the tone
could continue until the PIC turned it off.

Have you looked at all the data sheets and sample programs available
for the PIC from the manufacturer? It's been a long time since I looked
there, but I think there were sme good examples of what you want to do.
Paul, KD7HB