Develop a musical composition using both the specified melodic theme and the alphabetical pattern naming.
X:1
L:1/16
M:2/4
K:Bb
['B4 g2 b4 g2 f2e2ceBc f4 cB_AG']  
X:1
L:1/16
M:2/4
K:Bb
 f2 f4 cB | BcBGF2F2 | f2 f4 b2 | cfbg f4 | f2fe c4 | bcbgf2e2 | f4 A2>B2 | c2f2 c4 | B2Bcf2ff | 
 c4 b4 | g2>b2g2f2 | e2c2 B4 | g2 b4 g2 | f2e2ceBc | f4 cB_AG | F8 | g2>f2b2gf | e2dc B4 | 
 g2 b4 g2 | f2e2ceBc | f4 cB_AG | F8 |]  