BTC sound with a car horn?

Hi Guys,
I've heard of someone using a PWM sound through a drill and some other electric motors with microcontrollers and solid state relay or something.

Wondering what the feasibility would be of achieving this with a standard car horn?
I hear they are just a loudspeaker that has been turned into a buzzer, so if you short the contacts they are a loudspeaker again,
& just require a lot more current.

I can do the 1 bit PWM sound with Roman Black's BTC algorithm.

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