Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:4/4
K:D
['fg afge dfed cdec ABAG FAdf', 'eAAA Adfd']  
X:1
L:1/8
M:4/4
K:D
 fg | afge dfed | cdec ABAG | FAdf gfed | cdec A2 fg | afge dfed | cdec ABAG | FAdf gecd | 
 edde d2 :: cd | eAAA Adfd | eAAA Adfd | gfeg fedf | edcB AGFE | DFAc d2 cB | Acee a2 aa | 
 bgef gecd | edde d2 :|  