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
['cA (3AAA', 'fage fefg']  
X:1
L:1/8
M:2/2
K:D
 Ad d2 ecdB | Addc dedB | Adde fdeg | fage fdBG | Ad d2 ecdB | Addc dedB | Adde faed |1 
 cA (3AAA cBAA :|2 cA (3AAA cA (3AAA |: fdge fdge | fdge fd B2 | fage fefg | aA (3AAA aA (3AAA | 
 fdge fdge | fage fefg | abaf eged | cA (3AAA cBAA :|  