Rockbox

\note{You can control whether or not Rockbox includes the contents of

subdirectories when adding an entire directory to a playlist. Set the
\setting{Settings $\rightarrow$ General Settings $\rightarrow$ Playlist
$\rightarrow$ Recursively Insert Directories} setting to \setting{Yes} if
you would like Rockbox to include tracks in subdirectories as well as tracks
in the currently-selected directory.\\}

…

\subsection{Helpful Hints}

\subsubsection{Including subdirectories in playlists}
You can control whether or not Rockbox includes the contents of
subdirectories when adding an entire directory to a playlists.
Set the \setting{Main Menu $\rightarrow$ Settings $\rightarrow$ General Settings
$\rightarrow$ Playlists $\rightarrow$ Recursively Insert Directories}
setting to \setting{On} if you would like to include tracks in subdirectories
as well as tracks in the currently selected directory.