Develop a musical composition based on the provided pattern of letters and incorporating the given motif within it.
X:1
L:1/8
M:4/4
K:Bb
['B/B/B Bd', 'bBbB aBaB gabg']  
X:1
L:1/8
M:4/4
K:Bb
 B/B/B Bd fdfd | B/B/B Bd ecAc | B/B/B Bd fdfd | fgec d2 B2 :| bBbB aBaB | gabg fdcB | bBbB aBaB | 
 gabg g2 f2 | bdGb acFa | gBeg fdcB | B/B/B Bd fdge | dbca b2 B2 |]  