“Rumba box” is a name used in the English-speaking Caribbean for bass kalimbas. Typically in these instruments the player sits on the box, reaching down between his or her legs to pluck the tines. I’ve made several non-traditional variants, two of which are shown here. Most are chromatic, with tines made of spring-tempered steel rods or bars. On some of them the tines have been reshaped to adjust the tuning of the most prominent overtone relative to the fundamental, making a more coherent tone quality. Some have rattles on the tines. The rattles bring out the re-tuned overtone and give a distinctive edge to the tone.
The first instrument heard in the audio clip is a rumba box with rattles. It’s followed by a very large rumba box accompanied by percussion and winds.