What term describes the act of mixing or blending different elements together?

The term that best describes the act of mixing or blending different elements together is "commingle." This word specifically refers to the process of combining various components or substances into a single entity. It conveys the idea of merging distinct items, creating a unified mixture. In contrast, the other terms carry different meanings: "concomitant" refers to something that accompanies another thing, "commitment" relates to the act of dedicating oneself to a cause or obligation, and "connoisseur" describes an expert or a knowledgeable appreciator of a particular field or area, typically used in relation to fine arts or foods. Thus, "commingle" is the most accurate choice for describing the act of blending elements together.