Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
Q:1/2=80
M:2/2
K:G
['Sig.D in dB ec dB G2 dB', 'GBEB GBEB']  
X:1
L:1/8
Q:1/2=80
M:2/2
K:G
 G2"^Key Sig.D in MS" dB ec dB | G2 dB AFDF | G2 dBec dB | ecdB AFDF :: GBEB GBEB | GBEB AFDF | 
 GBEB GBEB | ecdB AFDF :|  