What characterizes a "theme and variations" musical form?

A "theme and variations" musical form is characterized by the presentation of a main theme that is subsequently altered in various ways throughout the piece. This involves taking the original melody and creating multiple variations that may change aspects such as rhythm, harmony, texture, or even the key, while still retaining the essence of the original theme. Each variation retains some likeness to the theme, allowing listeners to recognize the starting point while also enjoying the creativity that unfolds in its reinterpretation. This form is often employed to showcase the composer's creativity and technical skills in manipulating musical ideas, making it a popular choice in both classical and contemporary compositions.

In contrast, the options that describe a single melody repeated without changes, a dialogue between solo and ensemble parts, or strict adherence to traditional chord progressions do not align with the concept of "theme and variations," as they suggest a lack of development and variation which are central to this specific musical form.