Build an Action group using Export Configuration

I reported earlier I switched to tiny audio files as a way of taqging podcasts at the album level (/t/16895/1 It occurred to me several episode-level tags were fairly consistent across podcast albums (e.g., genre, composer, podcasturl).

This Export Config allows me to fill in any blank episode tags using the tiny file tags as the default. It builds an Action group. The steps are as follows: Maintain Master List of Composers (by Album) >> Run Export Config (in my case, against the tiny files) >> Run Action group. Result: Filled composer tags at the episode level.

Name: Action Group Generator-Composer Fill

$filename('C:...\Application Data\Mp3tag\data\actions\Composer Fill.mta',UTF-8)'[#0]'$loop(%album%)
'T=5'
'F=COMPOSER'
'1=$if($eql($regexp(%album%,'''''',),'''$regexp(%album%,'',)'''),$if(%composer%,%composer%,'$replace(''$replace(%composer%,,)'','''',)'),%composer%)'$puts(counter,$add(1,$get(counter)))

'[#'$get(counter)']'$loopend()

Sure beats manually maintaining an Action group.

Note: The above ACTION does not affect existing entries, only blanks. I use to indicate tags I really want to stay blank. The Regexp works around a persistent problem I've had with Mp3tag (/t/16547/1 of not being able to escape single quotation marks (') in FORMAT statements (e.g., Album = Kera's Think).

FORMAT statements (especially those as complicated as the one above) are SLOW. You might want to use filters to minimize the number of episodes touched by this ACTION group. For example I only use the Composer Fill ACTION group with the filter NOT composer PRESENT.

You can simplify the numbering of actions within the export loop ...

1: $loop(%ALBUM%)

2: '[#'$sub(%_counter%,1)']'
3: 'T=5'
4: 'F=COMPOSER'
5: '1=other stuff here ...'
6: $loopend()

... and check the number of single apostrophes in the formatstring expression in the export script, ...
my editor cannot display the scripting expression in the right coloured way.

... and please explain the sense of function $regexp() without applying a regular expression.

DD.20150515.1001.CEST

I have tried, but do not understand, please explain in other words ...
F=COMPOSER
1=$if($eql($regexp(%album%,'',),'Album C'),$if(%composer%,%composer%,),%composer%)

DD.20150515.0935.CEST

Sorry, should have attached an example with the 1st post.

Canterbury Christ Church University's Pu.mp3 is the tiny audio file I use to maintain album tags
Canterbury Christ Church University's Public Lecture Series - Total Policing. Using technology to fight crime.mp3 is a sample podcast
Composer Fill.mta is the Action group generated by the Export Config

So ... 1) run the export config on the tiny audio file, 2) get the action group, 3) run the action group on the sample podcast and 4) composer gets filled in the podcast (if it's blank).

I picked a podcast that has a single apostrophe in its album name, showing the need for the bastardization of the album name with regexp in the Export Config.

Canterbury_Christ_Church_University_s_Pu.mp3 (94.9 KB)

Composer_Fill.mta (204 Bytes)

Canterbury_Christ_Church_University_s_Public_Lecture_Series___Total_Policing._Using_technology_to_fight_crime.mp3 (28.5 KB)