Advice needed on adding tmcc and RailSounds to a RMT "1776" GG-1

You'd probably want the full sized Cruise Commander with that locomotive, so there is no logic trigger for aux sound.

One way to keep the special sound in the GG-1 is to wire it to the smoke output of the Cruise Commander.  That way you'd have remote control of the special tune, and you would also have all the standard sounds from the RailSounds Commander.

There is no "standard" way to wire the RSC to automagically keep a conventional horn.

Received this information today from RMT's Walter Matuch," Sound tune ("God Bless America" playing when horn button is pushed) is part of overall electronics system in that must be there to complete circuit. I do not know result of, if any, damage if removed."

So my question still is, Gunrunnerjohn, or anyone else, if I convert this locomotive to tmcc using ERR's full size Cruise Commander and add the ERR Railsounds Commander that's appropriate for GG-1 start up and running sounds, is it still possible for the "God Bless America" sound tune to be kept and activated by a tmcc button?

I'd have to see the electronics package to figure out if it could be used stand-alone.  Lots of stuff can be used in a "not as designed" fashion.