How is multiplexing on FM signals performed? How does multiplexing differ from FM signals to AM signals. If both FM and AM shift the message signal in frequency, then  is there a difference between multiplexing for FM or AM signal?
In U.S. broadcast FM, the various subcarriers (pilot tone, stereo L-R, RDS, etc.) are modulated into the upper sidebands (above the 15 kHz L+R/mono audio, but below 100 kHz, for instance 38 kHz DSB for the stereo subcarrier) of the baseband signal before that entire multiplex is used to wideband frequency  modulate a single, much higher frequency, FM carrier.

The FM carrier is modulated, but not shifted in center frequency.