Maybe this whole thing's a wild goose chase.
2 seconds sound clip from Scooby-Doo, Where Are You! - The Backstage Rag (S1E9).
You can hear this line at 00:15:00.848 in the Blu-ray version of the episode.
Quote context
[...]
- Well, come on. Let's get down below stage quick.
- What now? They're all empty. Not even violins in them.
- Maybe this whole thing's a wild goose chase.
- How about that man in the black cape? Explain him.
- And Scooby. He saw that man in the black, too, didn't you, huh?
- Somebody's playing the big organ on the stage.
- It must have been our imagination.
- Well, that was the first time I ever heard mine.
[...]