Take the sound file you want to make a horn, convert it to .raw (use google to find a convertor) Rename the sound file to horn1.raw and place the converted file into your data->snd folder. Make sure to backup the original horn 1.
Well, what file type is the sound file now? .wav? .mp3? on www.google.com
type the file type of the sound file then to .raw. So for example : .wav to .raw convertor. If you can type on this forum you can use google.
Okay okay, we'll burp you in a bit and change your nappy. Try this as a starting point. Or shall I download it, install it, make it for you, do your washing, and make your bed?