Try this link:
http://www.pentatonika.com/army.html
It has the music....
Play Bb Bugle open valves, play per the music written. It sounds best.
Valves 1&3 give "D" calvary bugle.
This is the biggest asked question in this forum, look under:
"Need Music for Taps" ...Dave. Over 5700 hits.
Play with passion, and bring a tear to the eye...you know you`ve done it well.
The best I heard was with an "Echo". A second player hidden away, and answers each phrase. Trick is to play a long held note for each phrase and DO NOT wait until the echo finishes, start playing as soon as he gets into that note.
All the best