Just to amplify a little on what Bob Bolton was saying-

The bugle is one of a number of horns that are called natural horns,because they only play the pitches in the harmonic overtone series of the fundamental--(Bb, for instance) the harmonics work pretty much like they do on the guitar, except (for some reason that I have never quite understood) the lowest pitch that you can play is actually the octave of the fundamental--

The notes that it plays, in the key of C (for all transposing instruments, the fundamental called C, even though it isn't) are (C)C-G-c-e-g-c-and so on, the first C being the note it doesn't really play--

The funny thing is, though, in the harmonic overtone series, the number of notes you can play doubles in each succeeding octave, One note in the lowest--Two notes in the second octave, Four in the third (which is where the bugle calls mostly are) eight in the fourth, and Sixteen in the fifth(if you could play there, which you can't)--

There is a particular style of Trumpet, used in Bach's time, called Klarinblasen, which used the notes in the fourth octave, which, through advanced lip-technique, the players could bend so that they corresponded to scale notes-

The third octave is the easiest to play in, though it doesn't have as many notes as the one above--

Military music is based on drum cadences-each military unit has it's own unique cadence, used for marching drills and parades. and, as the pipers among us know, for dancing--and bugle calls tend to simply use bounce through the octaves and major triad using one cadence or another(after a while, they tend to sound more alike than different)

Since brass music up until 1813 (when the valve was invented) was written within the limitations described above--and since they were widely used and written for from the sixteenth century, I am inclined to believe that most good music for bugles and other natural horns must have been pretty much written well before the Civil War--I mean, how many melodic possiblilities are there for the four or five notes in a two octave major chord?