Kitz is right.
Especially on a motor driven horn like the Ahoogah's.

For the little VW horns, they're 12V and don't draw enough current to warrant the addition of a horn relay.

I've been thinking of using double VW horns on my 31, makes em a little louder.

I still want an Ahoogah horn though and like you it'll be frame mounted.
Maybe at the rear of the car so you can reply to those friendly souls who honk their horn at you the millisecond the light turns green.

Then again, maybe a diesel air horn would be good there....