Warning - Be sure to read the warning at the bottom of this post.
There is something called a USB Locobuffer (MS100 replacement) made to work with Digitrax Loconet. And there is a program made by JMRI called "Decoder Pro" that is open source and uses Java as it's operating system. The developer uses a Mac to write the Decoder Pro products.
Decoder Pro will supposedly run on a Mac and let you program the sounds in any of the Digitrax decoders like the SFX064, the Sound-Bug and others. Both the sound-bug and the SFX064D or very powerful DC and DCC programmable sound cards. Using that combination you could, supposedly, load any sound project into those decoders, load individual sounds, change the keys that activate the sounds, set the volume level and other settings in the sound cards, etc.
Note that I said Supposedly. I am not a Mac user. I have tried to install the JMRI software on my PC several times over the years. At best I can get it to sort of function for a while. Then a new version of Java will load into my PC and I have to spend weeks corresponding with the developer to attempt to straighten it out.
I Have had no luck at making the JMRI software work with the Loconet/Digitrax products. Further I find the JMRI user interface entirely confusing. I do use the SFX064 and other sound cards from Digitrax and find them to be exciting new products with a lot of possibilities. User developed sound projects are popping up on the net and even some on the Digitrax site. This is a new generation of sound card, unlike anything else. I have used the Digitrax SoundLoader program and the chip manufacturers assembler to make some very interesting sound projects, but, those are only available for the PC.
While I find the JMRI stuff to be less than useful on the PC, you might have better success using the Mac since that is what the developer writes the code on. But, I can not say for sure if that is the case.
If you want to spend some time learning about the SFX sound decoders and figuring out how the JMRI software works, you will find the Digitrax SFX decoders to be very versatile.
As you can tell, I am not a big fan of Decoder Pro, but, for a Mac, it MAY be just what you need.
If I were you, I'd really look at the JMRI software, perhaps even call the developer and explain your needs, and verify it does what you need prior to spending any money on the hardware you will need.
Nah!, If I were you, I'd buy a PC /DesktopModules/NTForums/themes/mls/emoticons/whistling.gif
(Dont take this as a recomendation of any product, it is simply an avenue you might wish to persue.