Alan, this is the correct forum, except for maybe the DCC forum. The Echo Valley set is an HO set and Bachmann doesn't make S.
Paul,
I don't think the EZ-Command base included with the set allows you to change the whistle. EZ-Command is a very basic, low cost DCC base. From what I can see about it, it only lets you set up to 10 locomotive addresses, ring the bell, blow the whistle, speed and direction control.
The whistle selection is set by a CV (configuration variable) in the decoder and you'll probably need access to a more sophisticated DCC command base.
Rusty