The change for _multiartist is nothing to do with NAT, and you would probably not want %_multiartist%

You probably wouldn't want that - because %_multiartist% is designed to indicate where a *track* has multiple artists - which could be e.g. a duet on a non-VA album or on a VA album or on a NAT. The `$if($ne(%albumartist%,),%album%/)` is designed to complement the `$if2(%albumartist%,%artist%)` i.e. if we are using %artist% for the top-level directory rather than %albumartist% then it is probably a NAT track, and that is why I have used the same test (but expressed differently) for deciding whether to use the next directory down.

NOTE: I just realised another issue here - which is that %artist% could be e.g. "Elton John feat. Kiki Dee" - and we would probably want the primary artist here i.e. artists[0] but AFAIK there is no easy way of getting that reliably from a script variable at present. So, perhaps I should add a $index(multi-value, x) script function (x starts at 1 rather than the python 0) and use `$if2(%albumartist%,$index(%artists%,1))` for the top-level directory.