Final answer:
The artist who designed the Berlin Jazz Festival posters in the 1970s is not specified, but the style described is reminiscent of John Heartfield's photomontage approach to poster and propaganda art which was prominent in the 1930s in the Soviet Union. Like Alfonse Mucha's sensual posters, the festival posters may have utilized vivid colors and juxtaposed imagery to create a unique visual style.
Step-by-step explanation:
The designer of the Berlin Jazz Festival posters in the 1970s who incorporated photographic elements with unusual juxtapositions could be referencing an artist similar in style to the photomonteur John Heartfield. Heartfield was known for his participatory approach and photomontage techniques in poster and propaganda art, an art form which had gained significant prominence by the 1930s in the Soviet Union. Exhibitions celebrating the creative work of poster artists like Victor Deni, Vladimir Mayakovsky, the Kukryniksy, and others indicated the evolution of poster design from an artistic and propagandistic perspective. The posters of the Berlin Jazz Festival likely continued this tradition of visual storytelling.
Alfonse Mucha and artists like him used vivid colors and natural motifs to bring posters to life, replacing Post-impressionism with their own stylized approaches. The combination of visual repetition and limited motifs was both a method of aesthetic choice and a response to the stricter censorship and regulation that political posters underwent, according to the time and place of their creation.