Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
Q:1/8=160
M:3/4
K:D
['gf ed fa']  
X:1
L:1/8
Q:1/8=160
M:3/4
K:D
|:"Em" gf ed fa |"A" ge ed cA |"G" gf ed fa |"D" Ad dA FD ::"G" GB FA E2 |"A" Ee ed cA | 
"G" GB FA E2 |"D" Dd dA FD :|  