Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:3/4
K:D
['AA BAGFGE D2 F2']  
X:1
L:1/8
M:3/4
K:D
 AA | BAGFGE | D2 F2 FF | A2 G2 GE | B2 A2 AA | BAGFGE | D2 F2 FD | A4 AA | D4 |]  