Create a musical composition based on the alphabetic representation of the predetermined pattern and the given melodic theme.
X:1
L:1/8
Q:1/2=100
M:4/4
K:Bb
['B2 bg fdcB', 'BGFE DEFD']  
X:1
L:1/8
Q:1/2=100
M:4/4
K:Bb
 B2 bg fdcB | AFcF dFcF | B2 bg fdcB | FAce dB B2 :| BGFE DEFD | ECCG cGGA | BGFE DEFD | 
 B,BAc dB B2 :|  