If I understand your question, you want to send different frequencies from a single pin and have each frequency turn on a different LED or other action.
An easy way would be to use an LM567 tone decoder, which were used in old telephones (
https://www.ti.com/lit/ds/symlink/lm567.pdf). Reed relays, which were tuned to different frequencies, were also used. You might have a hard time finding them today.
My first choice, though, would be a chip with more port pins, particularly since you already are using an mcu.
John