Books have been written about this. Bachata is a variation on ancient Spanish/Latin American guitar music. Here's a snipet introducing one of the books:
"Derived from the Latin American tradition of guitar music, bachata emerged in the 1960s only to be denigrated by the media, mainstream musicians, and middle- and upper-class Dominicans, mainly because the lyrics?often about hard drinking, women troubles, illicit sex, and male bravado?were considered vulgar and worthless. While popular radio filled the air waves with merengue and salsa, bachata musicians were forced to develop their own system of producing and distributing their music."
Maria, I suspect you've heard bachata or one of it predecessors blaring from a cabaret as you were driven by it as fast as possible. But you probably didn't know what it was (or, as Jane notes, you may have known it as "amargue").
Brugal was not an option with classic bachata music. It was mandatory. Ay Dios I miss those days.