For evidence of this, listen to Benjamin Britten's War Requiem, which at times is immensely powerful, though not completely tonal.
From what I recall, and it has been a few years since I listened to the War Requiem, it is a marriage of musical innovation and the bardic skills of the poet. The central religious text is the Latin Requiem Mass. What Britten did which had not been done before in so extensive a fashion was to also include the poems of Wilfred Owen and provide a musical setting for those for those throughout the Mass as the voice of the soldier. It is this juxtaposition between life in war and the Mass for the dead which gives the piece so much power. As Owen was English, the poetry in the Requiem is sung in English how it was written, whilst Latin is retained for the traditional Mass. Britten's sensitivity towards setting both Mass text and poem is the thing which moves it from what could have been a gimmick into pure inspiration, no more, no less.
These are the poems that are used in each Mass section:
Anthem For Doomed Youth Autumn 1917
Voices or But I was looking at the permanent stars 1916
(believed to be the preliminary poem that led to Anthem For Doomed Youth)
The Next War Autumn 1917
Sonnet on seeing a piece of our heavy artillery brought into action Summer 1918
Futility Summer 1918
The Parable of the Old Man and The Young Summer 1918 (This is the poem that retells the story of Abraham and Isaac)
The End 1916-1918
At A Calvary Near the Ancre Early 1918
Strange Meeting 1918
The poems meet the themes addressed in each section of the Mass. For example, Strange Meeting depicts an English Soldier coming face to face with the German soldier he stabbed to death with his bayonet a few days before. Both soldiers are now dead. The poem finishes with the line:
"Let us sleep now"
which finds itself echoed in the Mass text by the Latin words of the Libera me:
"Requiem aeternam dona eis, Domine:
et lux perpetua luceat eis.
Requieescant in pace. Amen."
(Trans: Rest eternal grant upon them, O Lord:
and let eternal light shine upon them.
May they rest in peace. So be it.")
As a moving marriage between poetry, music and incorporating themes we can still, unfortunately relate to today, it is worth a listen.
The title page of the score has these words on it by Owen: "My subject is War, and the pity of War. The Poetry is in the pity.....All a poet can do today is warn."
The piece was completed by Britten in 1961.
I hope that this is of interest to some of you.