As the U.S. Army Bands website describes it, "Taps" "signals that unauthorized lights are to be extinguished. This is the last call of the day. The call is also sounded at the completion of a military funeral ceremony." It's the opposite of wake-up call "Reveille."
The most famous military bugle call also plays during flag ceremonies, and if you're not a veteran of the U.S. military, you might remember the signal to extinguish lights at the end of the day from Boy Scout or Girl Scout camp or a Memorial Day event.
As this classic audio clip from John Wayne's America, Why I Love Her albums explains, Union Army Brigadier General Daniel Butterfield and his brigade bugler Oliver Wilcox Norton get credit for the tune, a variation of earlier bugle call "Scott Tattoo." In 1862, "Taps" became a common way to signal lights out for both Union and Confederate units.
The new call remained part of United States military culture beyond the American Civil War.
In 1862, Captain John C. Tidball, West Point Class of 1848, started the custom of playing "Taps" at military funerals. It became a fixture of funerals and memorial services at Arlington National Cemetery and other final resting places of service members by 1891.
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Further, there's words to a familiar, minute-long tune more associated with bugles and drum taps, written by Horace Lorenzo Trim:
Day is done, gone the sun,
From the lake, from the hills, from the sky;
All is well, safely rest, God is nigh.
Fading light, dims the sight,
And a star gems the sky, gleaming bright.
From afar, drawing nigh, falls the night.
Thanks and praise, for our days,
'Neath the sun, 'neath the stars, neath the sky;
As we go, this we know, God is nigh.
Sun has set, shadows come,
Time has fled, Scouts must go to their beds
Always true to the promise that they made.
While the light fades from sight,
And the stars gleaming rays softly send,
To thy hands we our souls, Lord, commend.
For more information, read and watch the valuable works of professional bugler, Air Force veteran and "Taps" historian Jari Villanueva.