Final answer:
Unison refers to things corresponding exactly or happening in harmony.
Step-by-step explanation:
Unison refers to things corresponding exactly or happening in harmony. In music, it refers to multiple voices or instruments playing the same pitch or melody simultaneously. For example, a choir singing in unison means that all members are singing the same notes at the same time. Similarly, in an orchestra, when all instruments play the same notes at the same time, it is called playing in unison.