I must admit I fooled around with horns on an old subaru that had NO horn to speak of - often wasn't even heard. I just started adding whatever bargain bin junk -- and at some point an ooga horn. At the end, there were 4 mis-matched (un-tuned) horns + the ooga. It took some creative wiring. Eventually the ooga got a separate dash button for picking up the kids. The horn pad triggered all, the dash button the ooga only.
Pro's. I was heard in a panic when someone was about to hit me. It felt powerful to carry a "bigger stick."
Con's. While not train-horn loud, it was Too much. It would cause other cars to panic/flinch/lurch if I used it. I saw it causing an accident one day, getting someone hurt. So I pulled one or two out.
Who do you want to be in your community?
-m