Explain the difference between cross-hatching and impasto in creating a sense of texture. why would an artist select one over the other?

Impasto is a technique where paint is applied with heavy strokes and a lot of it with each stroke. It creates uneven texture with a lot of paint on purpose. Cross hatching is made by shading with two or more sets of intersecting parallel lines. This means that impasto is more useful when creating a sense of texture.

i'm not sure i completely understand your question, but i will do my best.

i think the answer you are looking for is sequence. (see below)

a repeated melodic fragment would be best defined as repetition, while repeated chords (different or the same) could be a chord progression. however, you then mentioned the chord and melodic fragment beginning on higher or lower pitches, in that case, the answer could be best defined as a sequence. the definition of a sequence is as follows: "the restatement of a motif or longer melodic (or harmonic) passage at a higher or lower pitch in the same voice."

let me know if this !