They were created to help speed up and simplify the process
of editing and composing drum parts in REAPER.
There are four note maps for each library: default, renamed,
unique, and minimal. All of them use Toontrack's default MIDI
mapping scheme, which is partially based on the GM Drums standard.
The "unique" and "minimal" note maps also prioritize the GM Drums
standard over a more logical grouping of each kit piece.
For more details on the hows, whys, and whats, check out the