Why hasn’t this been invented yet?
My wife came up with this idea about 6 years ago, but I am amazed that it is still not mandatory on every car.
It’s the sorry horn.
You use it when you make a mistake driving (eg you accidently cut someone off, or scare a pedestrian you didn’t see who has right of way). You just give them a toot with your sorry horn. It has a nice reassuring ‘sorr-ree’ tone that perpetuates a sense of calm in what could otherwise be a road rage scenario.
If you wanted to take it further you could develop a range of horns for different occassions. One for complimenting people on their car, another for congratulating a wedding procession, etc.