What common analogy is used to help explain the physics behind spectral shifting?

Answer

The pitch of a siren dropping as an ambulance moves away from you (Doppler effect)

The Doppler effect, specifically the dropping pitch of a siren as an object recedes, is used as a common analogy to explain how motion affects wave perception, relating to light's redshift.

What common analogy is used to help explain the physics behind spectral shifting?
galaxiesastronomyDistanceredshift