As Memorial Day approaches, a reminder about taps.
The bugle call, played on bugle or trumpet to sound daily lights out, or to honor the dead at military funerals and memorials, is written lowercase and roman. It is not a song, so capitalization and quotation marks are inappropriate.*
On this point, even the Associated Press Stylebook and I are in accord, and Wikipedia (Imagine!) is unreliable.
If, however, you are referring to the saccharine texts written to the music by Horace Lorenzo Trim ("Day is done, gone the sun" or "Fading light dims the sight"), then you may employ capitalization and quotation marks.
*Inappropriate is a euphemism for wrong.