What term describes a high, clear sound produced by stopping a string at its halfway point on a string instrument?

The term that describes a high, clear sound produced by stopping a string at its halfway point on a string instrument is "harmonic." When a player lightly touches a string at specific points (like the halfway point), it vibrates in a manner that produces a pitch which is an overtone of the fundamental note. This technique, often referred to as "playing harmonics," creates a bell-like tone that is distinct from the sound produced by pressing the string down completely.

The other terms relate to different musical concepts. Hemiola refers to a rhythmic pattern that creates a cross-rhythm, homophonic describes a texture where there is one main melody accompanied by chords, and hocket is a technique in which two or more voices or instruments alternate in delivering different parts of a melody, creating a syncopated effect. These concepts do not apply to the described phenomenon of producing high, clear sounds on a string instrument.