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
['', 'af g/f/e dc AF GB A/B/A/G/']  
X:1
L:1/8
M:2/4
K:D
 A |:"D" dA FA | de fe/f/ |"A" ed cd |"Em" ef gf/g/ |"D" af g/f/e | dc AF |"G" GB A/B/A/G/ |1 
"D" FD D2 :|2"D" FD De |:"D" ff/f/ fe |"G" g2 g2 |"D" ff/f/ fa |"Em" gf ef/g/ |"D" af g/f/e | 
 dc AF |"G" GB A/B/A/G/ |1"D" FD De :|2"D" FD D2 |]  