Which aspect of madrigals involves music depicting emotional words?

The correct choice is the concept of word painting, which refers to a musical technique where the music directly reflects the literal meaning of the lyrics. In madrigals, composers often used this technique to enhance the emotional impact of the text. For example, if the lyrics describe a rise in mood or a character's excitement, the accompanying music might ascend in pitch or tempo, thereby "painting" that emotion through sound. This creates a vivid connection between the words and the music, enhancing the listener's emotional experience.

Other aspects such as harmony, rhythmic variation, and melody inversion, while important in music composition, do not specifically relate to the direct representation of emotional words. Harmony involves the combination of different musical notes played or sung simultaneously, rhythmic variation relates to changes in the beat or pace, and melody inversion is a technique where the melody is altered by reversing the order of the notes. While these elements contribute to the overall structure and feel of a piece, they do not encapsulate the precise portrayal of text through music that word painting exemplifies.