Taps is a bugle call which is a signal, not a song. The signal was also known as the Drum Taps, The Taps, or in soldiers' slang: Taps.
July 1862, after the Seven Days battles at Harrison's Landing (near Richmond Virginia), the wounded Commander of the 3rd Brigade, 1st Division, V Army Corps, Army of the Potomac, General Daniel Butterfield reworked, with his bugler Oliver Wilcox Norton, another bugle call, "Scott Tattoo," to create Taps, thinking the regular call for Lights Out was too formal.
Military Taps was adopted throughout the Army of the Potomac and finally confirmed by orders. It wasn't soon after that other Union units began using Taps. It became so popular that even a few Confederate units began using it as well. After the war, Taps became an official bugle ca;;.
While not officially a song - these word are often sung to the tune -
Day is done, gone the sun,
From the hills, from the lake, from the skies.
All is well, safely rest, God is nigh.
Go to sleep, peaceful sleep, may the soldier
or sailor, God keep. On the land or the deep, Safe in sleep.
Love, good night, must thou go,
when the day, and the night need thee so?
All is well. Speedeth all To their rest.
Fades the light;
And afar Goeth day,
And the stars Shineth bright,
Fare thee well;
Day has gone, night is on.
Thanks and praise, for our days,
'Neath the sun, Neath the stars, 'Neath the sky,
As we go, this we know, God is nigh.
http://youtu.be/WChTqYlDjtI