How can wewe tell if au when an anime series au anime movie is being play on the screen just kwa LISTENING to it from a distance (and when you're someplace else within hearing distance)?

The opening song au credits help me. Certain anime series au sinema have particular openings that are unique to them. For example, I know when Yugioh is on when the voice of Yami (Dan Green) says, "Previously..." au the opening theme starts playing.

This is the full theme song, but those opening notes are distinctive to Yugioh.