Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:2/2
K:G
['e>A A2', "eaag abag eaab c'bag"]  
X:1
L:1/8
M:2/2
K:G
 gf | e>A A2 egfg | e>A A2 e2 dB | G2 BG dGBG | Bdef g2 fg | e>A A2 egfg | e>A A2 e2 dB | 
 GABd g2 ga | bagb a2 :: ag | eaag abag | eaab c'bag | eggf gage | dega bgag | eaag abag | 
 eaab c'bag | edef gage | dBGB A2 :|  