I heard a story once. As a matter of fact, I've heard a lot of stories in my time. They went along with the sound of a tinny piano playing in the parlor downstairs.

11 seconds sound clip from the Casablanca (1942) movie soundboard.

You can hear this line at 00:50:06 in the Blu-ray version of the movie.

Quote context

[...]

- A very great and courageous man.

- He opened up for her a whole beautiful world full of knowledge and thoughts and ideals.

- Everything she knew or ever became was because of him.

- And she looked up to him and worshiped him with a feeling she supposed was love.

- Yes, that's very pretty.

- I heard a story once. As a matter of fact, I've heard a lot of stories in my time. They went along with the sound of a tinny piano playing in the parlor downstairs.

- Mister, I met a man once when I was a kid, they'd always begin.

- I guess neither one of our stories is very funny.

- Tell me who was it you left me for?

- Was it Laszlo, or were there others in between or aren't you the kind that tells?

[...]