Many Digitrax SoundFX decoders come with two different sound schemes pre-installed. Check the decoder instruction sheet for which sound schemes are installed in the decoder you are using. Instruction sheets are available on this website on the product pages for each decoder.
The decoders come from the factory with CV60 programmed to a value of 01 to play the default scheme. If you want to play the other pre-installed sound scheme, simply program CV60 to a value of 00. You can switch back and forth between the two schemes. Changing CV60 does not erase either pre-installed schemes.
If you want to download a different sound scheme into the decoder, you will erase the pre-programmed schemes. These are available on the website should you wish to restore them at a future date so, feel free to experiment with different sound schemes!
For example, the SFX064D plays an SD38-2 diesel scheme by default. It also comes with a generic steam scheme pre-installed just in case you want to use it in a steam loco. If you want to use the generic steam scheme, you'll need to program the CV value for CV60 to 00. To reselect the default SD38-2 scheme, program CV60 to a value of 01.