Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:4/4
K:G
['', 'gDGB fGeG dDGB dDGB cDFA', 'fdef gdBd ecAG FAd^c d^def gGBd fGeG']  
X:1
L:1/8
M:4/4
K:G
 (3def |: gDGB fGeG | dDGB dDGB | cDFA dFAd | fed^c edef | gDGB fGeG | dDGB dDGB | cDFA f3 e |1 
 d^c=cF G2 (3def :|2 d^c=cF G2 (3Bc^c |: dgfg bgdB | ceag fdef | gdBd ecAG | FAd^c d^def | 
 gGBd fGeG | dDGB dDGB | cDFA f3 e |1 d^c=cF G2 (3Bc^c :|  