Video by PG Music Inc. via YouTube
Source
The Playable RealTracks feature allows you to add MIDI notes to a RealTrack, using the Hi-Q instruments. Playable RealTracks can be edited in either the Notation view or the Pianoroll view. This video is specific to the Notation view.
More info on the Playable RealTracks feature in the PianoRoll can be found in this video at 9:00: https://youtu.be/BS0yuTwhcCc?t=540
Playable RealTracks in the PianoRoll are also demonstrated in this video: https://youtu.be/z3r85Sj2wfA