Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:2/4
K:D
['', 'dc/B/ AF FE/F/']  
X:1
L:1/8
M:2/4
K:D
 d/B/ |:"D" Ad dc/B/ | AF FE/F/ |"G" GB BA/G/ |"D" FD D2 | Ad dc/B/ | AF FE/F/ |"G" GB"A" BA | 
"D" D2 D2 ::"D" dA/d/ fa |"A" ge e/f/e/d/ | cA/c/ eg |"D" fd f/g/f/e/ | dA/d/ fa |"A" ge ed | 
"A" cb"G" ba |"D" d2 d2 :|  