Which musical technique involves the use of repetitive motifs that are gradually changed?

The correct answer is minimalism, as this musical technique is characterized by the use of repetitive motifs that undergo gradual changes and variations. Minimalism emerged in the mid-20th century, primarily in the context of Western art music. Composers like Steve Reich and Philip Glass are key figures known for utilizing this technique, where simple melodic fragments are repeated and transformed over time, creating a sense of evolution in the music while maintaining an overall clarity and focus on the original materials.

In minimalism, you might find motifs that undergo subtle shifts in rhythm, harmony, or dynamics, sustaining listener interest through these incremental changes. This approach contrasts with other styles, which may rely more heavily on elaborate development or broader harmonic structures.

The other techniques listed, such as impressionism, serialism, and expressionism, focus on different compositional goals and methods, highlighting aspects like atmosphere, predetermined sequences of pitches, or emotional expression rather than gradual repetition and transformation. Understanding minimalism allows listeners to appreciate how simplicity can lead to intricate and engaging musical experiences.