Spent a prep period with these lines in my head and an ink brush in hand. Sassoon was an officer in the Royal Welch Fusiliers during the Great War, and wrote Everyone Sang shortly after the armistice. It's generally interpreted to be a reaction to the ceasefire, but I like to remember that communal singing was common in the trenches, and his critic Robert Graves notes that while such singing was generally limited to popular music hall numbers and army rallies, Welsh soldiers more often sang hymns, and in their native Cymraeg.
Everyone suddenly burst out singing;
And I was filled with such delight
As prisoned birds must find in freedom,
Winging wildly across the white
Orchards and dark-green fields; on - on - and out of sight.
Everyone's voice was suddenly lifted;
And beauty came like the setting sun:
My heart was shaken with tears; and horror
Drifted away ... O, but Everyone
Was a bird; and the song was wordless; the singing will never be done.