Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:9/8
K:G
['dBB dBc BAG', 'e2 a abg fed g2 d cdA']  
X:1
L:1/8
M:9/8
K:G
 dBB dBd BAG | EAA cAB cde | dBB dBc BAG | A2 B ABG FED | dBB dBc BAG | EAA cAB cde | 
 dBB dBc BAG E2 G AGF G2 F :: EBB BcA | BcA Bcd | e2 a abg fed | g2 d cdA BdB | c2 E A2 G FED | 
 E2 B BcA | e2 a abg fed | g2 d cdA BdB | c2 E A2 G FED :|  