What the heck is the derivation of the phrase “blow the horn” in a car. From the stage coach days?
Perhaps today we should say, “Activate the vehicle’s warning device.”
Archaic, as “dial the phone,” I suppose.
Yes, it comes from the days when coach drivers had an actual horn and had to blow on it to signal they were approaching.
As for me, I always say “Honk the horn.” I don’t know where “honk” comes from, though.
It still makes sense. When you “blow the horn”, you are triggering a small pump that, literally, blows air through a horn.
I don’t think I’ve ever heard that phrase in that context. I don’t think I’ve heard it even in a musical context, where it makes more sense.
Really? In this day and age i would have supposed it was MP3 sound 
That makes me wonder, what actually makes the sound in a car horn? Does it have some sort of reed?
Cars don’t have air horns. They just have diaphragms actuated by an electromagnet, connected to a horn-shaped resonance chamber. (Actually, modern cars usually have two horns at different frequencies, to produce a more perceptible interval.)
In any case, it’s not a wind instrument; just a specialized loudspeaker.
Thank you.
Didn’t the older horns sound like geese?
The word ‘honk’ is onomatopoeic.
Except for cars that do in fact have air horns - a few upmarket models still have them as standard, I believe, but they’re commonly fitted as an aftermarket modification.
And of course if you go back far enough you do have air horns blown by a rubber bulb…
I remember an episode of “Maude,” and Mrs. Naugutuck was relating something about her date the previous night. You have to imagine this in her voice, increasing in crescendo, where she said (something like), “At midnight we were going to BLOW THE HORN!”
I’m a gonna let you blow the horn;
I’m a gonna let you blow the horn;
A oorah, a oorah, a oogah, oogah,
I’ll take you riding in my car.
Like this.
After her knee replacement surgery, her grandson mounted one like that onto her walker. She had quite a lot of fun with it.
The number of roadworthy cars that have actual air horns is so vanishingly small as to make this the zenith of nitpickery. I’m sure you could find a car with square wheels if you looked hard enough. 
Busine or coachmans long horn. Blown to announce the coach by the driver or ‘shotgun’ rider [coachmans assistant]
Square wheels? in Canada of course “as is tradition”
Of course, the really upmarket ones have horns that play the first couple of bars of “Dixie”. 
Tangential, but posted here because this is the thread that started the train of thought that led to me learning this particular fact:
There’s a forum for jerks who put train horns on their vehicles. I like to think that my fellow man is basically a good and decent soul, but then I find out that there’s a place on the internet that basically exists so that jerks can get together and talk about how awesome it is that they’re jerks. sigh