I have taken a closer look at the files.
The problem seems to be with how JRiver interprets padding at the end of the song or album name in the id3v2 tags.
The following file, for example, has two 00 bytes at the end of the album name "That's Right". In JRiver I then see a semicolon.
0000050: 4200 0000 0f00 0000 5468 6174 2773 2052 B.......That's R
0000060: 6967 6874
0000 5443 4f4e 0000 0006 0000 ight
..TCON......
In contrast, in the following file there is no padding so there is no semicolon.
0000030: 6e74 7279 5441 4c42 0000 000d 0000 0054 ntryTALB.......T
0000040: 6861 7427 7320 5269 6768 7454 434f 4e00 hat's RightTCON.
Here is a sample file.
semicolon.mp3Thank you for your suggestions as to how to fix this. Wouldn't these suggestions, though, just affect the display of the tags? The semicolons would still be there, and JRiver would add semicolons when writing back to the file.
Any chance this could be changed? I am not sure whether or not these tags can be considered valid id3v2 tags or not, but it nevertheless seems strange to add the semicolons.