using tagFormat to display composer as artist

[adrian]

I just updated to minimserver 2.1 and when I activated the new recently added and recently played features, Running with full license. I got this error from minimwatch (using the command line):

>restart
stopping MinimServer[echidna]
MinimServer[echidna] is stopped
MinimServer[echidna]: incorrect tag name 'composer' in option 'Artist.displayFormat' in property 'tagFormat'
MinimServer[echidna] error: now stopped, use 'restart' or 'close'

I have set

tagFormat=Artist.displayFormat={$composer^^: $artist}

so that when a composer is listed I get, the composer and artist listed, but otherwise just the artist. But it appears that I am not allowed to use $composer. I tried setting it to simply {$composer} and get the same error, but if I set it to simply {$artist} then I get no error. (Is composer a nonstandard tag?) I set this up years ago and don't have much classical music. It looks like I tagged classical music so "composer" is the composer and "artist" is set to "conductor / orchestra", as in "Sir Adrian Boult / London Philharmonic Orchestra"

How do I get the result I want, where classical music displays composer, conductor and orchestra and other music just the name of the artist?