This relief "Herz-Rhythmus" (Heart-Rhythm) was made in 1966. Mack used gypsum which he arranged in rhythmic structures on a wooden panel and painted it in gold. The calm motion pattern, which is primarily made up of vertical indentations, creates harmonious structure of light and shade, an effect that is even increased by the golden coloring. The integration of light into the work's aesthetic effect allows ever new impressions and associations owed to the changing light incidences at different times of the day.