Kokichi, Himiko, Korekiyo and Shuichi were singing the caged child to do the Seance.

All: “🎶At last, at last, at long, at last. Young guard dog and little lost girl sealed with an iron cage.🎶”

The others were, idk, doing stuff? (I only watched the trial and googled up the lyrics and ritual name. Just edit this to let the AI know what the others were doing. It was pitch black in the room as Tenko was in the cage.)