Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:6/8
K:C
['AGF FCB, A,CF ABc BBA BGF', 'F2 B AFA cag fdd d2 c']  
X:1
L:1/8
M:6/8
K:C
|: B | AGF FCB, | A,CF ABc | BBA BGF | EGE ccB | AGF FCB, | A,CF ABc | BBA BGF | EGE F2 :: B | 
 AFA cag | fdd d2 c | dcB Bgf | ec_c =c2 B | AGF cca | BAG g2 f | e2 c efg | fgf f2 :|  