He's singing, sir.
4 seconds sound clip from the Trading places (1983) movie soundboard.
You can hear this line at 00:30:18 in the Blu-ray version of the movie.
Quote context
[...]
- It's a whirlpool bath sir. I think you'll enjoy it.
- They're very musical people, aren't they?
- What shall I do with his clothes, sir?
- He'll have to have something wear back to the ghetto, after I've won our bet.
[...]