This is John Chambers' very experimental collection of music for assorted "sessions". Each session has its own subdirectory, whose name should be Capitalized. The lower-case subdirectories here that are named for rhythms and/or dances are places to link files that may be useful in more than one session.
Some tools to do useful things in directories full of .abc tune files:
Session lister (Names, Titles) -- Collection lister -- Tune lister