Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/16
M:3/8
K:G
['B2B2B2 d>c A4 A2A2A2 c>B G4 B2A2G2', 'D4 A>B A2A2 d2 A4 B>c B2B2', 'D>d d4 D>d']  
X:1
L:1/16
M:3/8
K:G
|: B2B2B2 | d>c A4 | A2A2A2 | c>B G4 | B2A2G2 | G>F F4 | A2G2E2 | E>D D4 :| A>B A2A2 | d2 A4 | 
 B>c B2B2 | e2 B4 | d>e d2d2 | e4 d2 | (3(cdc) B2A2 | G4 D>d |: d4 D>d | d4 D>d | (3(cdc) B2A2 |1 
 G4 D>d :|2 G6 |]  