As we're all aware, R* was out of touch during development of GTA V. This for example is reflected in a large downgrade in terms of vehicle horn variety in comparison to the prequel. Instead of putting some effort and time to give us an excellent experience from horns of the vehicles, the developers choose the laziest path they ever could - that is, to create short lists of horn groups shared across all vehicles, which removed any kind of variety or character from certain vehicles.

With this modification however, your experience from pushing that horn button will incomparably increase, whereby nearly every vehicle will have its own, unique horn, with any randomizations completely removed.
Most of the horn configurations are leftovers from GTA IV, but for the sake of number of vehicles in the game, there's a large chunk of horns that were created from scratch.

Many of the DLC vehicles are currently unsupported. This might change in an update on condition that there's enough demand.

This (https://docs.google.com/document/d/12OnKhV7t608LcSOsgkpMUQHH8Vc3MZpP9Dx8qtPqhDM/edit?usp=sharing) document contains a list of assigned horns with their respective vehicles. There's also a linked video which you can use to preview some of them.

Installation is done in the same manner as all other mods that involve adding a DLC.

Happy honking!