我々は声をそろえて歌を歌った。

we

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

voice

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to collect; to gather; to get together; to complete (a collection); to arrange; to put in order; to prepare; to get ready; to make uniform; to make even; to match

song; classical Japanese poetry (esp. tanka); modern poetry

to sing; to sing (one's praises in a poem, etc.); to compose a poem; to recite a poem