What did Charles Baudelaire mean by correspondences between the senses?

In the work of Charles Baudelaire, particularly within his collection Les Fleurs du mal, the concept of correspondances refers to the interconnectedness of sensory experiences—such as harmonies, tones, and colors—which allow the poet to evoke the underlying mystery of existence.1

Baudelaire’s theory suggests that the physical world is not merely material but contains a "dark and confused unity" that can be glimpsed through subjective emotional responses. By treating these sensory impressions as interrelated, Baudelaire influenced later Symbolist poets, who adopted this concept to "orchestrate" their poetry. They utilized the inherent qualities of words to create musical and sensory patterns, aiming to communicate the ineffable intuitions of the human inner life rather than relying on traditional, descriptive expository functions.1