Cannot be done with sound card or software. These are subcarrier s in
the FM signal. One has to tap the receiver after the demodulator and
send through a separate LF FM receiver ("adapters"_. Note that there are
legalities to consider in the US.
----------------------------------------------------

hmm.... new question I'm now wondering about after reading the above.

Does this mean that any audio tape I recorded years ago of regular FM
stations that happened to broadcast subcarriers also have the
subcarrriers recorded on my old tapes????

And if I was able to buy an SCA decoder, I would be able to hear these
old SCA transmissions when listening to my old audio tapes?

or would my old audio tapes only have the regular FM station information
recorded on them, even though the FM station was broadcasting a
subcarrier that I was unaware of at the time?