Identify the dominant musical element that defines the structural form of the
piece.

Incomplete question. However, I provided some of the dominant musical elements common today.

Explanation:

They are:

Melody

Harmony

Key

Metre

Rhythm

1. Melody refers to the tune of a particular piece of music. So it encompasses variations in pitch that are carefully selected to form a shape or music pattern.

2. Harmony is an element that combines chord or triad in other to harmonize a melody.

3. A key is a way of grouping the different pitches into a common group. These groupings are made possible when using a music instrument liked the guitar.

4. Metre is a way of combining ‘beats’ in a particular moment of time during vocalization. There may be a strong accent in the first beats with milder accents on later beats.

5. Rhythm is a way of combining instruments and vocalization into a meaningful hearing experience.