Generate a piece of music. It is monophony.  
X:1
T:Music21 Fragment
C:Music21
L:1/8
Q:1/4=108
M:2/4
I:linebreak $
K:D
V:1 treble 
V:1
 A | AA FA | BA F z | F E3 | F E2 A | AA FA | BA F z | E2 FE | D2 z A | AA FA/A/ | BA F z | F E3 | %12
 F E2 A | AA FA/A/ | B/B/A/A/ F z | E2 FE | D3 z | D>D FA | d3 z | B>B dB | A3 F/G/ | AA F/F/A/A/ | %22
 BA F2 | EF/G/ F/EE/ | D4 || %25  