Antonyms for the phrase "be in unison" include be discordant, clash, contradict, differ, disagree, disapprove, dissent, mismatch, oppose, and vary. Being in unison implies harmony and agreement, but these antonyms suggest a lack of agreement or harmony. For example, if a group of people are not in unison, they may have conflicting opinions, ideas, or viewpoints, resulting in discordance or disagreement. Being in unison is important in various settings, such as music, sports, or teamwork, where synchronization is necessary for success. On the other hand, understanding and acknowledging differences among individuals can also lead to creativity and innovation.