FREQOUT can do dual frequency (polyphonic), and that is a mess at 4MHz.
DTMF works the same way, but I’ve never had a telephony system understand it for a pic clocked less than 20MHz, no matter what I do.
For a single frequency it might be ok, but as said, PWM is non-blocking, can make the sound forever, and a much better choice for a single audio freq.