My assumption is that, for digital albums, the only legal way to acquire the music is to buy from the publisher.  And that once the publisher stops selling it, there are no other options.

Is that right, or are there other, legal ways to go about it?

My question is specifically motived by this album:

http://vgmdb.net/album/46317

which has a second track that's available only by digital download.  Square Enix has discontinued hosting for that download, and so it's no longer available

I'll admit, what's particularly peeving is, the download was originally free, as far as I know.  As a result, if someone were to share it, technically it would cost the publisher nothing (even if opportunity costs are counted).  But I'm fairly certain this is not allowed...

Law and Logic are very unrelated. I can't help you.

You needed to have a Japanese Square Enix Members account in order to be even able to download this (you had to have been able to register the points card to prove that you bought the album or had entered any of the codes from the previous SQ series albums in order to qualify).  That would present a significant barrier to non-Japanese language fans. I think there are websites that describe how one can get a Japanese Square Enix Members account but it's after the fact now and I think they're changing their rewards program anyways as there has not been any news on that front for quite some time.

I agree, it would have been hard for me to get this download through normal channels.

That said, the same is also true for retailer bonuses, event-only releases (e.g. sampler CDs), albums which require club membership, etc.  Though through the "magic" of the secondary market, physical items like these become relatively easy to get.  It seems like only the digital stuff remains "off limits," if you will...

Just doing some searching, legal rulings in the US seem to forbid selling digital music, without authorization of the original publisher:

http://www.npr.org/sections/money/2013/ … ge-says-no

This doesn't seem too surprising.   It would be difficult to know, for example, after selling a copy of a digital song, that the original was actually deleted.