you can use a 567 to demodulate FSK (such as radioteletype) audio. the oscillator's frequency limit is 500khz, so it's not a good choice for modulating or demodulating FM. most FM demodulators work at 10.7Mhz (and depending on the application, on other RF frequencies as well). all of the LM56x PLL devices made in the 1970s and 1980s were generally limited to 1Mhz or less maximum operating frequencies. PLLs can modulate or demodulate FM, but a 567 isn't a good choice.