To see the total Duration -- total playing time -- of a playlist (or view), select the tracks to be totaled:
In the navigation tree, click on the playlist/view, but do not then click on a track. MC treats the selected playlist/view as selecting the entire set of tracks.
-OR-
In the navigation tree, to see any tracks subset (such as all the songs by an artist, or in an album, or whatever), click on that group in the tree.
-OR-
Within a playlist/view, select ALL the files (Ctrl+A).
-OR-
Or, select any desired individual tracks to create an arbitrary set of songs.
-THEN-
Look at the bottom bar of MC's window. Whenever a track is selected, MC shows facts about it. When multiple tracks are selected, MC shows totals at the bottom: total number of files, the total size of the files, AND the total Duration in hours:minutes:seconds.
(One oddity, at least in my MC: The order of the bottom items is different if it's about one track vs. a set. Selecting one track shows title, format, duration, file size; Selecting a set shows total files, total file size, total duration. The difference is the positions of duration and file size get reversed.)
