Which term is used for a nonharmonic tone performed immediately before resolving to a chord tone?

The term that refers to a nonharmonic tone performed immediately before resolving to a chord tone is known as an appoggiatura. This musical term describes a specific type of nonharmonic tone that typically approaches a chord tone by leap and resolves to it by step, creating a temporary tension before reaching a stable pitch within the harmony.

In the context of musical composition, appoggiaturas are often used expressively in melodies, adding emotional weight and color. They are usually not part of the underlying harmony but instead create a momentary dissonance that enhances the resolution to the consonant chord tone.

The other terms mentioned refer to different concepts in music theory: diminution refers to the elaboration or decoration of a melody, neighbor tones are nonharmonic tones that move stepwise away from a chord tone and return to it, and acciaccaturas are very short, grace-like notes that precede a main note. Therefore, the use of the term appoggiatura is appropriate for describing this particular musical function.