Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
Q:1/4=200
M:2/2
K:D
['fdaf df A2', 'AdAd BdBd']  
X:1
L:1/8
Q:1/4=200
M:2/2
K:D
 fdaf df A2 | Bdce dfeg | fdaf df A2 | Bgec d2 d2 :: AdAd BdBd | cece dfdf | AdAd BdBd | 
 ceAc d2 d2 :|  