When a locomotive has ARN on it and you edit it in CCP the numbers will not show up in Trainz and have thread exceptions but if I wanted to edit the horn sound how could I do it without tampering with the ARN script?
Find the horn sound you like and note the kuid number, open the asset in Explorer *(not ccp).
Change the kuid number, dont forget to alter it in the kuid list at the bottom as well.
If the asset comes up faulty afterwards you can revert to original.
That's why I'm saying change it in Explorer and not CCP.
In fact clone the asset first and alter it. If the clone doesn't become faulty you can change the original and delete the clone.