TuneStacker needs to know how long each song is in order to build well-timed program logs. The Song Lengths sub-tab scans your audio files and writes the duration of each one into the library's Duration field — quickly, accurately, and without any manual effort on your part.
You'll typically run this once after a fresh import, and again any time you add a significant batch of new files. Songs that already have a Duration value are updated only if the file has changed.
Click Go!. That's really all there is to it. Librarian works through every entry in your library, opens each audio file just long enough to measure it, and writes the duration to the library. The musical note animation in the status bar lets you know it's working.
The scan runs in the background, so you can keep browsing the song list and working in other parts of the app while it runs. The status bar shows a running count as files are processed.
On a large library, this scan can take a few minutes. The app is completely usable while it runs — you don't need to sit and watch the musical note bounce around, entertaining as that is.
Duration values are stored in seconds. A song that's 3 minutes and 42 seconds long gets a Duration value of 222. TuneStacker reads these values when calculating how many songs fit in a given hour and whether the log will run long or short.
If a file can't be read — because it's missing, corrupted, or in a format macOS can't handle — Librarian skips it and logs a note in the status bar. The rest of the scan continues normally.
After the scan, you can find any songs that still don't have a duration by using the filter in the middle pane. Set the field dropdown to Duration and type unset in the filter field. Any songs that came up empty will appear in the list.
Songs with no duration are usually missing their audio file, or the file is in a format that couldn't be read. Check the file path in the Attributes tab and make sure the file actually exists at that location.
Duration values are measurements of the actual audio file, not the EOM or Cue markers you set in the Transitions tab. A song's Duration represents its total length from start to finish; EOM is where AutoCast begins the transition to the next song. Both values matter, and they're stored separately.