Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/16
M:2/4
K:G
['AB c4 B4 A2AB AGEF G2GE DEGA', 'G2 (3DEF GABc d2ef gfge dBGB c2ec']  
X:1
L:1/16
M:2/4
K:G
 AB | c4 B4 | A2AB AGEF | G2GE DEGA | BcBG AGEG | c2ec B2dB | AGAB AGEF | GFGE DEGA | BcBA G2 :: 
 (3DEF | GABc d2ef | gfge dBGB | c2ec B2dB | AGAB A2GE | gfgd efgf | edcB AGEF | GAGE DEGA | 
 BcAB G2 :|  