with one voice

alternative in one voice

1. In unison, together

   But when they knew that he was a Jew, all with one voice about the space of two hours cried out, Great is Diana of the Ephesians.

   1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], →OCLC, Acts 19:34

   1 more example

   Seven boys stood in a row all ages, all sizes, all yellow-haired and blue-eyed, all in full Scotch costume, and all smiling, nodding, and saying as with one voice, "How are you, cousin?"

   1875, Louisa M[ay] Alcott, chapter 2, in Eight Cousins

2. broadlyidiomaticIn a mutually agreeing or like-minded manner; concordantly, unanimously.

   Unfortunately, the global political community is a long way from speaking with one voice on anything, and climate change is no exception.

   2007 December 1, Bryan Walsh, “Can We Save the World by 2015?”, in TIme

   2 more examples

   The nobles around Prince John implored him with one voice to throw down his warder, and to save so brave a knight from the disgrace of being overcome by odds.

   1819, Sir Walter Scott, chapter 12, in Ivanhoe

   Well—Jean went down and asked his father and his mother and his old grandmother if they would permit him to marry Mlle. Malo; and they all with one voice said they wouldn't.

   1916, Edith Wharton, Coming Home, section 3