Another Passover-inspired Civil War fact: The African American spiritual "Go Down Moses," aka "Let My People Go," was sung during the War by enslaved blacks who took their freedom by fleeing to Fort Monroe, a Union army stronghold in Virginia.
The song was published by a chaplain who heard it there, and became popular in the North. It is sometimes credited as the first black spiritual, although I'm a little dubious about counting publication by a white chaplain as the marker of what was the first black spiritual; whoever was singing this song when they arrived at Fort Monroe probably knew other spirituals as well, and no one can carbon-date which was sung first.
"Go Down Moses" remains one of the best known and most sung of the early African American spirituals. For many people, the song seemed to capture a moral righteousness they believed the Union could and should claim (although publication of the song pre-dated the Emancipation Proclamation, and even the fate of the "contraband" fugitive slaves who'd stolen their own freedom by fleeing to Fort Monroe was not permanently settled at that point).
While visiting the Union encampments in Virginia, Lincoln reportedly joined in prayer meetings at which "Go Down Moses" aka "Let My People Go" was sung. It was subsequently performed by the Fisk Jubilee Singers
in the 1870s, by Paul Robeson
in the early twentieth century, and by many Jews at Passover seders over this past weekend.
Please note that it would be incorrect to assume that Lincoln also chanted the Four Questions while visiting Union encampments, nor was he known to have broken into a rousing rendition of "Dayenu."