Hello from Hummelstown, PA! (It's near Harrisburg.)

I've been researching the notion of hacking together an mp3 doorbell,
and a websearch hit on the PJRC website. Btw, yes, I noticed the bit
about not being available anymore. Frankly, I can't see that the mp3
player industry drove sales _that_ low - aren't there enough hackers out
there to keep things going somewhat?

Thus, I might be interested in buying a used unit.

I need to know exactly what these units can do. E.g. can it be triggered
it to play 1 file and stop (as opposed to continuous)?

Does it merely play files from a list, or can it be set to randomly pick
a file?

Can I adapt USB hardware to it (to use a flash drive - just to make it
easier when I want to add files)?

I'm sure that there are other concerns to see if it's practical for my
application.