Answer:
A chorale prelude is a short instrumental composition based on a hymn tune that reminds the congregation of the hymn's melody.
Step-by-step explanation:
As it is stated, a chorale prelude is a brief composition to be executed by an organ, which is part of a chorale melody. Thus, it is implemented as an anticipation of the grupal singing of the chorale itself. And even though it is a prearranged composition, it is also characterized by improvisation.