Sometimes, for personal preference or technical reasons, an assets dependencies may need to be replaced. Described here is an example of how to change a Locomotive's hornsound relatively easily and quickly by using CCP or editing the config.txt file.
CCP Screen, tag is highly controlled, so CCP limits edit flexibility. Good for this sort of task.
Open Content Manager Plus (CMP) via the Trainz launch screen.
Search for the locomotive you are wishing to change.
Right-click on the item, go to 'Edit in Content Creator Plus'.
You may be asked if you want to continue due the content item being from a different Trainz version. It is usually safe to continue, but there are warnings that this can cause a faulty asset. Backup or clone the asset if you are unsure.
In CCP scroll down and you will see the line 'hornsound' amongst other things, e.g. 'enginesound', 'enginespec', 'description' etc.
Click on the '...' button that allows you to scroll through your entire collection of assets. Narrow it down using the drop down menu filter and locate a new hornsound of your choice.
Exit CCP, saving as you go.
Commit the asset before you return to Trainz.
If you wanted to, or if the instability of CMP/CCP forces you to, you could always use the manual method, which is just as easy.