Sorry to add to the issues list, but I have been working with the import and export "write" functionality recently. My aim has been to be able to edit the tags either in Muso or in Mp3tag in a consistent way, by having an Mp3tag "clean-up" action. Running this action either after an export or before an import ensures that the metadata is consistent wherever it was edited. I have hit a slight snag:
My first "classical music tagging" scheme set the GroupHeader to the opus or work and the Title to the movement. This required an import action for Title since the Title in the song file included the opus (in the format "opus: movement") so that opus would appear on the SB touch / iPeng etc. My new version of the scheme aims to simplify as much as possible and to reduce the number of import actions (I was hitting the limit). Since Muso will look for repeated phrases in titles and create GroupHeaders accordingly, this seemed like a smart move (although, as previously reported, while Muso correctly does not duplicate the GroupHeader on the desktop display, it does duplicate it in the "remote control" view).
Here's the problem: when Muso writes out the tags it does not use the same logic as when it imports them - instead the Title is written out as "GroupHeader: Title", regardless of whether the Title already includes the GroupHeader. Thus the song file now has "GroupHeader: GroupHeader: Title" as its Title tag. I would have thought that the Title should be checked for a matching phrase with GroupHeader, and stripped of it, before writing out "GroupHeader: Title".
EDIT:
OK I see what is happening here. Muso works fine if you manually import "opus: movement" into the Title and manually confirm the GroupHeaders on import - it strips the opus from the title on import and recombines on export - OK. What doesn't work is if you supply a ready-made opus field and import that to GroupHeader. The Album Page will display it as if the GroupHeader has been stripped, but it is clear (in "edit tracks") that it has not been stripped in the database. I think what is needed is to strip the GroupHeader from the Title on import (not export), so that the underlying field is the same as the album page display. This would not only fix this reported problem, but also fix the "remote control" problem.
Title tags
Re: Title tags
erm.... if you could give an example (of what Muso is doing with the tags on import and what you think it SHOULD do) that always helps 
Re: Title tags
I'll try...
I'll use the same example as in the other current query about Album Artists (the Dvorak quartets).
The Song file has the following tags (1st song):
TITLE String Quartet No13 in G, Op106: 1. Allegro moderato
WORK String Quartet No13 in G, Op106
MOVEMENT 1. Allegro moderato
If I import Title (as is) with no custom import actions, I can set the GroupHeading as "String Quartet No13 in G, Op106" in Muso, click "confirm" and it will remove it from the Title, leaving just "1. Allegro moderato".
If I import WORK into GroupHeading, then I get the following:
You can see that the title does not have the GroupHeader stripped from it, but when displaying the album page, Muso recognises that the GroupHeader appears in the Title and does remove it from the displayed title - see the following:
If you try and set the GroupHeader within Muso, you get this:
As you can see it adds the common part of the Title to the imported GroupHeader so that the suggested GroupHeader is doubled up.
I can get round the problem by importing MOVEMENT into Title, but now I have two (arguably unnecessary) import actions.
What is needed is for an imported GroupHeader to act in the same way as confirming a GroupHeader manually - i.e. stripping the matching text (and colon) from the title.
Alternatively, maybe an option to automatically confirm the GroupHeader (as being the common text before a colon), when importing - that would eliminate both custom import actions?
I'll use the same example as in the other current query about Album Artists (the Dvorak quartets).
The Song file has the following tags (1st song):
TITLE String Quartet No13 in G, Op106: 1. Allegro moderato
WORK String Quartet No13 in G, Op106
MOVEMENT 1. Allegro moderato
If I import Title (as is) with no custom import actions, I can set the GroupHeading as "String Quartet No13 in G, Op106" in Muso, click "confirm" and it will remove it from the Title, leaving just "1. Allegro moderato".
If I import WORK into GroupHeading, then I get the following:
I can get round the problem by importing MOVEMENT into Title, but now I have two (arguably unnecessary) import actions.
What is needed is for an imported GroupHeader to act in the same way as confirming a GroupHeader manually - i.e. stripping the matching text (and colon) from the title.
Alternatively, maybe an option to automatically confirm the GroupHeader (as being the common text before a colon), when importing - that would eliminate both custom import actions?
Re: Title tags
In 2.3.02: When prepending group header to title tag on writing, ensure group header not doubled up.
Re: Title tags
I've been testing 2.3.02. It does remove duplications between groupheading and title, but goes a bit OTT. It seems to remove the duplication on writing wherever it is in the title, not just the first words. For example I have a track with GroupHeader = "Salve regina" of which the first movement (Title) is "Part 1: Salve regina, salve mater". Muso strips out the Salve regina and gives me " Part 1: , salve mater" when it exports. My (and I think the generally accepted) convention is to follow a GroupHeader by a (single) colon, so only removing duplication which accurately matches the first part of the title before the first single colon should work best. (I emphasise single colon, to differentiate it from the double colon for subheaders - that wants to stay in the header).
Re: Title tags
This should be resolved in 2.3.04