Sorry about the Rally air horn, not very helpful as you can't get them at your local parts store. Got a bit over excited as I was re-packing the parts stash.
I've had air horns in the past, loud and great on the road but didn't like them as they had a delay which defeats the purpose.. Not good when someone starts to back up in the car park, as 0.5 second would really count
on the Hella super tones as thinking about it misses has them fitted on her Landrover by the PO, really great for single track lanes with blind bends