How many albums, composers, and performers are in my collection?

I have MP3tag displaying a directory with over 4200 tracks of classical music, created by dozens of composers, scores of performers, and parts of hundreds of albums. I'd like to know if there is a way to identify, at any given time, how many different albums are in my collection, assuming that each different name in the album field represents a different album. For some works, a different album would also be indicated by having different performers, even though the names in the album field is the same. For instance, I have different albums for "Beethoven: Symphony #5" performed by Karajan and Kleiber.

Similarly, I'd like to know how many different composers are listed in the "composer" field, and how many performers I've identified in the "album artist" field.

You could filter for files with the track number 1 and see how many files appear - this should equal the number of albums.

For the other fields, you would have to use an export with e.g. with $loop(%artist%,1) and then use %_total_files% at the end of the loop to get the number.
Please be aware that MP3tag does not compare the contents of fields in different files so that MP3tag does not detect any change in the data.

Thanks for your suggestions.

Unfortunately, track numbering is absent for many items, and does not start at number 1 for the first track of many other albums. Any other ideas?

Can you point to an article/post which tells how to create the type of export query you describe?

Load all files,
select all files and apply this quick&dirty export script to get the albums:

$filename(Album.txt,UTF-8)
$loop(%album%,1)$num(%_counter%,3) %album%
$loopend()

Create a new export in File>Export>new
and replace the whole sample script with just the suggested 3 lines.
Save the script,
execute it and view the result in a text editor.
I am pretty sure that you can edit the script so that the modification shows artists, preformers, composers