Yes it is. It’s a composite signal. You can break out the video and audio carriers separately, but the signal is created within the same modulator.
No, it is not. The sound in a US NTSC television signal is modulated separately from the video on a separate carrier spaced 4.5 MHz up from the center frequency of the video carrier.
An audio-only application that uses both frequency- and amplitude-modulation (but not on the same carrier) is FM stereo radio.
By far the most common implementation is the Zenith/GE pilot-tone multiplex system, which involves a sum signal (L+R channels, to provide compatibility with mono radios) up to ~15kHz, and a difference signal (L-R) amplitude-modulated onto a 38kHz carrier. The 38kHz carrier is suppressed before the transmitter to reduce the RF power required to transmit a given audio level. A lower-level 19kHz pilot-tone, phase-locked to the original 38kHz carrier, is added to the modulating signal, and recovered via a phase-locked loop in the customer’s stereo receiver. The RF carrier frequency is then frequency-modulated by the overall signal containing:[ul]
[li]0 to 15kHz: (L+R) mono audio.[/li][li]19kHz: pilot tone.[/li][li]23kHz-38kHz: lower sideband of (L-R) audio.[/li][li]38kHz-53kHz: upper sideband of (L-R) audio.[/ul][/li]The bandwidth alloted to an FM stereo broadcast is greater than for AM mono for at least three reasons:
[ol]
[li]The audio bandwidth is 15kHz, compared to 10kHz (or less).[/li][li]The addition of the (L-R) channel requires additional bandwidth for the modulating signal, up to 53kHz total in the standard implementation.[/li][li]Frequency modulation is inherently higher-bandwidth than amplitude modulation. The frequency spectrum of a carrier amplitude-modulated by a sinewave contains just the central carrier (f[sub]carrier[/sub])and two components at (f[sub]carrier[/sub]+f[sub]modulator[/sub]) and (f[sub]carrier[/sub]-f[sub]modulator[/sub]), whereas the spectrum of the same carrier frequency-modulated by the same sinewave contains the central carrier (f[sub]carrier[/sub]), plus paired components at (f[sub]carrier[/sub]+/-f[sub]modulator[/sub]) as with AM, and also at (f[sub]carrier[/sub]+/-2f[sub]modulator[/sub]) and (f[sub]carrier[/sub]+/-3f[sub]modulator[/sub]) and so on to infinity (although by far most of the energy is in the first two harmonics, so the RF is bandwidth-limited before transmission and FM stereo radio stations can be spaced 200kHz apart on the dial without much interference).[/li][/ol]
As would be expected, it takes a higher bandwidth to transmit and receive an FM stereo signal than an FM mono signal. In fringe conditions stereo FM may be noisy, and bandwidth-limiting the detector to pass only the (L+R) signal may provide a better listening experience (“the wider you open the window, the more dirt flies in”).