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
['e2 d2', 'BAGA BAGA']  
X:1
L:1/8
M:2/2
K:D
 defg a2 gf | e2 d2 e4 | ABcd edcB | ABcd e4 | defg (f/g/a) (gf) | e2 d2 d | fedf edce | d4 D4 :: 
 AGFG AGFA | AGFG A4 | BAGA BAGA | BAGA BdcB | AGFG AGFG | AGFG A2 (ag) | fagf edce | d4 D4 :|  