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 d']  
X:1
L:1/8
M:2/2
K:D
 B |"D" BADA"G" dADA |"D" BADA"A" defd |"D" BADA"G" dADc |1"D" dBAf"A" e2 d :|2"G" dbaf"A" e2 d |] 
 d |"D" dfaf"G" bgaf |"D" dfaf"A" (3(gag) fe |"D" dfaf"G" bgaf |"D" dBAf"A" e2 dd | 
"D" dfaf"G" bgaf |"G" bgaf"A" g2 fg |"D" agfe"G" dBAB |"G" dbaf"A" e2 d |]  