how does the bugle produce different notes?

Answer 1

The bugle produces different notes the same way that a trumpet (or any other brass instrument) produces different notes. All brass instruments are essentially just long tubes that amplify the vibration of the lips, called the embouchure. The faster the lips vibrate, the higher the pitch that is produced.

Without valves, a bugle can ONLY produce a single "series" of pitches. These pitches are called a harmonic series. There's a good explanation of this on Wikipedia: http://en.wikipedia.org/wiki/Harmonic_series_%28music%29

Most bugle music is written as if the bugle's fundamental pitch were a C (regardless of the actual pitch produced). Following that tradition, the bugle can play the following notes:

Pedal C - C - G - C - E - G - B-flat (usually this pitch is skipped as it's very flat) - C

Above the high C the "partials" get so close together that you can play almost any note...but it's not easy to play that high, so most bugle calls stick to the 5 notes C - G - C - E - G.

For instance taps is GGC, GCE, GCE, GCE, GCE, CEGECG, GGC.

Answer 2

In the position of the players lips. Tighter, looser, etc.