the FEF 4-8-4 was manufactured as DC analog
see: http://www.spookshow.net/loco/katofef.html
the DCC and Sound decoder were added, or you added them?
it would then be based on what decoder was/is going to be installed
being an ESU it depends if it is "dual mode" or not
which can be determined by the product item number or name
as in:
ESU/LokSound
We are pleased to offer the excellent ESU LockSound sound decoders, inluding "V4.0", "Micro 4.0" , the "Select", "Select Direct" and "Micro Select" models for American prototypes. The excellent features of ESU-decoders are even more enhanced by the addition of sound functions. That’s made possible through the award-winning LokSound technology. LokSound decoders are available for various applications, depending on gauge or digital system. When you order a LokSound decoder, we must know the specific sound file that you would like downloaded to the decoder. Instructions and lists of sound files are included on each type of decoder's catalog page. (Available "Select" models are each listed separately in our catalog.)
the above being a description of possibilities w/ ESU from a hobby shop website.
I hope this helps.
sincerely
Gary