Through the extended fields editor, I add the field "UNSYNCEDLYRICS". Then I copy & paste the lyrics for that song. After pressing "OK", I return to the extended tag overview and all looks fine (see attachment "MP3Tag (1).png":
Then I press "OK" and return to the MP3tag main window. Looking at the lyrics in the "Lyrics" column, I find it prefixed with the string "eng||" (see attachment "MP3Tag (2).png").
It it is not possible to remove this string and to keep the lyrics, after each editing the prefix "eng||" is added again. The only way to get rid of it is to remove the entire tag.
I have previously added lyrics to other songs and not observed the effect. Could it be caused by portuguese characters in the lyrics (i.e. "ã" and "ç") ?
I am using version 2.45a and Windows XP SP3 (english).