This audio signal can be heard separate from the video, using standard analog FM radios equipped with the appropriate tuning circuits.

A very frequent use of these circuits is in the tuning circuits of analogue radios.

This FM audio signal could be heard using standard radios equipped with the appropriate tuning circuits.

A capacitor whose capacitance can be varied is used in the tuning circuit of radio and television receivers.

This reflected the radio receiver application of filtering as Q was a measure of the frequency selectivity of a tuning circuit.

This error voltage is then fed back to the tuning circuit in such a way that the tuning error is reduced.

This resulted in fewer tuning circuits and the absence of a wave-change switch.

On a practical level, which I'm sure will interest you, they're used in industry for electrical tuning circuits.

Examples include the swings of a pendulum clock, the tuning circuit of a radio, and the heartbeat while resting.