Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:2/4
K:Bb
['ccdb c4 ff/d/cd f4 cd c2 cfdf/f/']  
X:1
L:1/8
M:2/4
K:Bb
 ccdb | c4 | ff/d/cd | f4 | cd c2 | cfdf/f/ | c2 dg | b2 bg | ffgd | c4 |]  