Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:2/2
K:D
['(FG) A3 (B AF)DF (Bd)cd (AF)DF G2', 'A2 (cd) e3 (f ec)Ac (ea)^ga (ec)Ac']  
X:1
L:1/8
M:2/2
K:D
 (FG) | A3 (B AF)DF | (Bd)cd (AF)DF | G2 BA F2 AF | G2 E2 E2 (EF) | DFAc d2 (df) | edcB A2 d2 | 
 cecA BdB^G | A2 A2 A2 :: (cd) | e3 (f ec)Ac | (ea)^ga (ec)Ac | d2 fd c2 ec | d2 B2 B2 (3ABc | 
 (dc)dA (BA)GF | GABc d2 (cd) | (BA)GF (GB)AG | F2 D2 D2 :|  