Final answer:
Modulation in music refers to the change from one key to another within a composition. The modulation that occurs in bar 83 requires a score analysis of the specific musical piece.
Step-by-step explanation:
To answer which modulation occurs in bar 83, we need to refer to the context of the musical piece in question, since bar numbers are specific to individual works. Modulation in music refers to the change from one key to another within a composition. When discussing modulation, it's important to distinguish it from the term 'frequency modulation (FM),' which is a term used in physics related to sound wave properties, as well as a method used in radio broadcasting. Assuming the context is indeed musical, modulation is observed when the tonal center of a piece shifts, which can be identified by changes in the accidentals not typically found in the original key or by a pivot chord that functions in both the original and the new key. An expert analysis of the score for the specific piece is required to determine the exact nature of the modulation without additional context.