TRAIN QUESTION! what would happen in this scenario?

most trains will have 2 or 3 horns anyways, in Britain they're used one and then the other to form what's known as '2-tone' and the American 'chime whistle' style horns often have 3 actual horns at least. I'd've thought that if one fails then the other(s) would either continue to function or could be operated separately.