Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:6/8
K:G
['B c2 e', 'dcB A2 B c2']  
X:1
L:1/8
M:6/8
K:G
|: d3 dBd | G2 B c2 e | d3 dBd | A2 B c2 e | d3 dBd | G2 B c2 e | gfe dcB | A2 B c2 e :: gbg dBd | 
 gbg dBd | gbg dcB | A2 B c2 d | gbg a2 c' | bag fed | gfe dcB | A2 B c2 e :|  