I've just started using Plex, a local and remote (over the internet) jukebox program. One hangup I've encountered deals with the length of a track.
Plex correctly displays the length of most tracks, but with live concerts, I use MergeMP3 to create a gapless version as well. Unfortunately, that program carries over all the tags from the first track in the sequence, so Plex displays the same "Duration" for the complete concert as for the first track (once you start playback, it does show the correct length on its internal player).
I fired up MP3Tag to change the value in the duration tag, and found that it didn't have a duration tag but did had a Length tag - which already had the correct value! I tried renaming it to Duration, but that appeared to only apply to MP3Tag's onscreen interface.