Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
M:4/4
K:G
['gdgb agab gdgb agef gdgb agbg gedB', 'gedB ABGA']  
X:1
L:1/8
M:4/4
K:G
|: gdgb agab | gdgb agef | gdgb agbg | gedB AB G2 :: gedB ABGA | BGAB cdef | gedB ABGA | 
 BGEB A2 G2 :|  