Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
Q:3/8=112
M:6/8
K:G
['d3 e3 d2 c BdG GgG GgG', 'g3 A3 B3 A2 G FAD DdD']  
X:1
L:1/8
Q:3/8=112
M:6/8
K:G
 d3 e3 | d2 c BdG | GgG GgG | F2 A AFD | d3 e3 | d2 c BdG | GgG GgG | f>ef g3 || A3 B3 | A2 G FAD | 
 DdD DdD | Ddc B3 | B3 c3 | B2 A GBE | EeE EeE | Ee^d e3 | e3 g3 | B2 c dDD | E3 c3 | F2 G AFD | 
 d3 e3 | d2 c BdG | GgG GgG | f>ef g3 |]  