Develop a musical composition using both the specified melodic theme and the alphabetical pattern naming.
X:1
L:1/4
M:3/2
K:Bb
['B G2', 'd g']  
X:1
L:1/4
M:3/2
K:Bb
 B G2 D TG2 | B G2 B A/B/c/A/ | B G2 D TG3/2 B/ | A F F c A/B/c/A/ :: G g{a} g ^f g2 | 
 d g Tg3/2 a/ b g | d g (a/g/)f/=e/ Tf2{ef} | A F F c A/B/c/A/ :|  