Regex first character Alphabet only

[ohrenkino]

In general: if you want to rename a folder, then use an action of the type "Format value" for _DIRECTORY.
BUT: as you do not want to rename just the current folder but also the parent folder, you will be left with empty folders after the process.
Only the current folder level can be renamed.
Also, I would apply a full path like
d:\music\1\ %artists% \ %album% (%year%) \ %artist% - %title%.ext
in order to get the same starting point.
(instead of the "1" insert the regular expression)
And finally, the field ARTISTS is no standard field - there are ARTIST and ALBUMARTIST. Are you sure that you have that field filled in in every track if you reference that in your string?

See also here:

Script for first letter groups for folder names

There have been a couple of posts on this topic, e.g. here, but I thought I'd share my solution to creating a folder grouping of a certain number of letters, using the first letter of a sort field (falling back to main field if empty). This is useful for players that struggle with long lists, like in a car. The formula produces the letter group folder name that you can include in your complete file path when doing a tag - filename action, e.g. "E:\Music\Classical\A-D\Bach, Johann Sebastian..." …