[pavel_lishin]

I wonder if they've done any research on what sort of recording keeps people on the line the longest.

[sharkweek]

I'd like to offer you a job in our marketing org

[flashman]

I would guess fake ringing tones, because the victim would think the phone hasn't been picked up yet. Animal Farm might work once or twice for curiosity's sake, but eventually people will cotton on. With a fake ring tone, they'd keep dialling until someone picks up.