IPA: /ˌæntɪˈfɒnəli/
KK: /æn'tɪfənəli/
In a way that involves alternating responses or singing, typically in a call-and-response format.
The choir sang the hymn antiphonally, with one side responding to the other.
Antiphonally → It is formed from "anti-" (meaning against or in opposition) and "phōnē" (from Greek, meaning voice or sound) and the suffix "-ally" (meaning in a manner). The word describes a manner of singing or chanting in opposition or alternation, typically in a call-and-response format.
Think of voices that are 'against' or 'in opposition' ('anti-') to each other, creating a beautiful harmony in a call-and-response style.