The base is original from the producer (chords and melodies), but is complemented with elements that complement the song that come from samplepacks, usually, vocal chops, guitars, wobbles sections, glitch effects. It is the standard in which most of producers work, in a project you will find MIDI files made by the producer, but also melodic loops.
Slow RnB beat with a synth bass instead of an 808.
Sample pack Off Balance by Pelham & Junior (Splice)
Loop name PJ_OB_Keys_loop_2_Soft_Grand_81BPM_Bbm.wav