Articulations specify how individual notes are to be performed within a phrase or passage.

Articulations are described in an editable text file with .rcCTRL extension in one of these locations:
Windows: C:\Users\<user name>\Documents\RapidComposerV3\DB
OS X: ~\Documents\RapidComposerV3\DB

Each library or virtual instrument requires such an .rcCTRL file that defines the possible articulations, arranged in groups.

An articulation can be a key-switch or a controller value change or both. It can be assigned to a phrase, or individual phrase notes, or even a track can have its default articulation.

E.g. if you open “Garritan Personal Orchestra 4.rcCTRL” you’ll see that there are articulations with just key-switch or controller change or with both as in
group=“GPOSoloStrings”; articulation=“Legato”; keyswitch=“C-1”; ctrl=68; ctrlval=127;

“group”: articulation group
“articulation”: articulation name
“keyswitch” (together with “keyvelocity”, optional): specify keyswitch note as note name (C4=MIDI note 60) or MIDI note number (0-127)
“keyvelocity” (together with “keyswitch”, optional): specify note on velocity for the key switch (0 is a note off event!)
“ctrl” (together with “ctrlval”, optional): MIDI controller number (0-127)
“ctrlval” (together with “ctrl”, optional): MIDI controller value (0-127)

The author will gladly help to create an articulations definition file, assuming there is a specification.