Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:6/8
K:D
['', 'fed edB AdB AFE', 'dfa afa baf dfd fef edB']  
X:1
L:1/8
M:6/8
K:D
 de |: fed edB | AdB AFE | BAG DEG | ABd edB | fed edB | AdB AFE | BAF DFA | Bdd d3 :| dfa afa | 
 baf dfd | fef edB | ABd edB | dfa afa | baf dfd | fef edB | Add d3 :|  