Generate a piece of music.  
X:1
T:Music21 Fragment
C:Music21
L:1/4
M:none
I:linebreak $
K:none
V:1 treble 
V:1
{/C} G G{/F} E F | E C2 B, | G, G, B,2 | C C E F ||{/F} E F G B | c B ^F G | %6
 G G E2 =F E/ D/ B, C || %7  