Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:2/2
K:Bmin
['B3 c', 'fg afge dcdB |1 ABde fdec :|2']  
X:1
L:1/8
M:2/2
K:Bmin
 B3 c dBAF | B3 c dfed | B3 c dcdB |1 ABde fded :|2 ABde fdec |: dfaf bfaf | dfaf g2 fg | 
 afge dcdB |1 ABde fdec :|2 ABde fded ||  