Develop tuneful melodies adhering to the specified letter notation and including the supplied thematic aspect.
X:1
L:1/8
M:4/4
K:G
['GFGB dBga bgaf gdBd', 'Bdgf gdBd']  
X:1
L:1/8
M:4/4
K:G
|: BA | GFGB dBga | bgaf gdBd | cAAG AEAB | ceag fdcA | GFGB dBga | bgaf gdBd | cBcA Bdeg | 
 fdcA G2 :: dc | Bddc d2 GA | Bdgf gdBd | cBcB A2 ag | fd (3ded cAFA | Bddc dBGA | Bdgf gdBd | 
 cBcA Bdeg | fdcA G2 :|  