All bugle calls used in So Ra No Wo To appear to be derived from Japanese calls.
This is the morning bugle call played by both Rio and Kanata and is heard in episodes 1, 2, 3, and 4. Kanata is eventually able to perfect this bugle call during episode 4 after struggling during the first three episodes. The origins of this bugle call are from the Imperial Japanese military, and was actually used up until the end of World War II.
This was the bugle call played by Rio after the team destroys one enemy tank during the simulation during episode 5. The origins of this bugle call are also from the Imperial Japanese military as it was the bugle call to signal an assault or attack on the enemy.
Presently, this particular type of bugle call is no longer used by most militaries around the world, which alludes to the fact that technology for electronic forms of communication i.e. radio do not work, or have been lost in the So ra no wo to world..
End of Schoolwork/Lessons/Official DutiesEditKanata plays this bugle call in episode 10 at sunset. Unlike previous bugle calls, this particular one is in use by the Japanese Self Defense Forces. This call is played at 1700 hours (5:00pm) and signals the end of the
official duty day, or for military academies and training sites, the end of training for the day.
Since this particular bugle call has no equivalent in the Imperial Japanese bugle call list, it is speculated that the Defense force one was chosen instead.