Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/4
M:4/4
K:G
['B A', 'B{c} B/A/G/A/ B']  
X:1
L:1/4
M:4/4
K:G
 G/A/ | B B A G | E E/F/ G E | D D E/F/G/A/ | B A A G/A/ | B B A G | E3/2 A/ G E | D D E G | 
 G2 G || B/A/ | B/A/ B{c} B/A/G/A/ | B e e c | d B{c} B/A/G/A/ | B A A G/A/ | B B{c} A G | 
 E2 G G/E/ | D D E F | G2 G ||  