A genre of 2/4 vocal and instrumental music that originated in Santiago de Cuba as part of the trova tradition. This genre gained widespread popularity around Latin America and continues to thrive. The bolero first spread from the east of Cuba to the Dominican Republic. In the early 20th century, the bolero reached Puerto Rico and Mexico, where it was popularized by the first radio stations around 1915.
By the 1930s, when Trío Matamoros made famous its mix of bolero and son cubano known as bolero-son, the genre was a staple of the musical repertoire of most Latin American countries. In Spain, Cuban bolero was incorporated into the copla repertoire with added elements from Andalusian music, giving rise to the so-called bolero moruno. The frequent fusions of the bolero with other Cuban rhythms are one reason why it has been so fertile for such a long period. 1880s– .
Bolero (Cuban)
I've listened to many of the links you have posted. Some of them were difficult to listen as the tonality was not comfortable to me. They were interesting but not easy to listen. I suppose we are habituated to certain kinds of music. Bolero is wonderful and I could listen a long time.