Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:6/8
K:D
['G ABA AFD dfe (d2 c) BGB', 'd2 f afd dfa bge efg (fa)(f']  
X:1
L:1/8
M:6/8
K:D
 G | ABA AFD | dfe (d2 c) | BGB dA(F | G)EE E2 G | AFA dc(d | B)GB (e/f/g)e | agf ed(e | f)dd d2 :| 
 | f | afd dfa | bge efg | (fa)(f g)e(d | e)cA A2 G | Fdd cee | dff efg | (f/g/a)(f e)d(e | 
 f)dd d2 :|  