jemplode but it won't locate my player(s) via USB
Jemplode only works via ethernet, if I recall correctly. Connect to the player with ethernet to retrieve your files.
my 1TB back-up HDD had just died, along with my music files which appear irretrievable
By definition, the drive in question was not a back-up drive, since it contained the only copy of your music files. I would call that an external or secondary drive, specifically one that has not been backed up.
what is it with hard drives these days?
Agreed that hard disks die a lot. I recommend backing them up.
they barely last a year or so...
That depends on
the brand you buy, and how you care for the drive.
Recently the drive in my laptop died because I dropped something small on the laptop at exactly the right spot at exactly the right time, enough for it to crash the heads. (Luckily I had it backed up.) Other things that can make a drive die are letting it get too hot or too cold. Or they can Just Die if they're Seagates.
I spent some extra money and got a Solid State Drive for my laptop, in hopes that it will be more reliable. But I still back it up, and the most critical data I back up to multiple places.