What it is
The requinto is bachata's first, lead guitar: small and tuned high. It's the voice of bachata — you know the style from the requinto's first notes.
The strokes
The requinto plays single chord notes (root, third, fifth) and dyads.
In the derecho it plays the chord's arpeggio up and down in eighths; in the majao, short answers to the singer; in the mambo, a repeating riff: the requinto takes the solo.
What a dancer hears
The requinto is the melody you dance to musically: its phrases tell you where to accent or pause. In the mambo, when the singer stops, it leads — time for the most striking moves.