There ya go, Will!
Lots of experience around here. Horns, among other items, pull a lot of power. A simple relay is nothing more than a switch to permit, perhaps, power directly from the battery to 'honk' the horns. Your handlebar button will simply activate the relay - sort of a lower-power electrical switch.
Ever notice on an older car how the headlight switch, after awhile, would get pretty warm? All that power flowing through the switch and then to the lights. Often the switch would fail due to wiring failures. Relays fix all. Simple, too.
I added relays to the headlight system on my 1986 VW Cabriolet and I had instant brighter lights and a cool dash switch. Old car guys do the relay deal on lots of things... horns, elec radiator fans, lights...
Get the horns, then ask us about a relay hookup. Often, horn kits include a relay and wiring tips.
Monte