What is meant by "ostinato" in musical terms?

Ostinato refers to a musical phrase or rhythm that is persistently repeated throughout a piece or a section of music. This technique provides a foundation over which other melodies or harmonies can be built, creating a sense of continuity and can contribute to the overall mood or structure of a composition. The repeated element can be melodic, rhythmic, or both, and it often serves as a driving force in various genres of music, including classical, jazz, and pop.

In contrast, the other options describe different concepts in music. A complex chord structure relates to the harmonic framework of a piece rather than the idea of repetition inherent in ostinatos. A style of singing in a slow tempo focuses on performance technique and expression rather than on repetitive motifs. Lastly, harmonizing melodies involves layering different pitches to create harmony, which also does not capture the essence of repeated phrases that define an ostinato. Understanding the role of ostinato can enhance a musician's appreciation of structure and texture in music.