Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:4/4
K:G
['', '(3def gdBd G2', 'AB cAFA DFAc']  
X:1
L:1/8
M:4/4
K:G
 (3def |: gdBd G2 (3def | gdBd G2 AB | cAFA DFAc | ed^cd B2 (3def | gdBd G2 (3def | gdBd G2 AB | 
 cAFA DFAc |1 B2 G2 G2 (3def :|2 B2 G2 G2 GA |: BGFG DGFG | BGFG D2 AB | cAFA DFAc | ed^cd B2 GA | 
 BGFG DGFG | BGFG D2 AB | cAFA DFAc |1 B2 G2 G2 GA :|2 B2 G2 G2 z2 ||  