Develop a musical composition based on the provided pattern of letters and incorporating the given motif within it.
X:1
L:1/8
Q:1/2=74
M:2/2
K:Bb
['B2 dB GBFB', 'B2 fB']  
X:1
L:1/8
Q:1/2=74
M:2/2
K:Bb
|: B2 dB GBFB | EBDB ED C2 | B2 dB GBFB | Egfe dBB z :: B2 fB gabg | fdcB Ac c2 | B2 fB gBbB | 
 fdcB FB B2 | B2 dB GeFd | EcDB ED C2 | DBEc FdGe | Agfe dB B2 :|  