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
['d2 c Bdc A2 B GEC E2', 'DFA dcd', 'A FGA']  
X:1
L:1/8
M:6/8
K:D
|: d2 c Bdc | A2 B GEC | E2 D DEF | GFE AFD | d2 c Bdc | A2 B GEC | E2 D DEF | GFE D3 :: AFA DFA | 
 dcd B2 G | GFG EGA | cBc A2 F | AFA DFA | dcd B2 G | BGB ABA |1 GFE F2 D :|2 GFE D3 |: DFA dcd | 
 edc B2 A | FGA A2 G | EFG G2 F | DFA dcd | edc B2 A | FGA ABA | GFE D3 :|  