Craft a piece of music that integrates both the suggested theme and letter-based structure.
X:1
L:1/4
Q:1/4=100
M:4/4
K:G
['G F E', 'G B']  
X:1
L:1/4
Q:1/4=100
M:4/4
K:G
 D | G F E G | F E D A | B G A F | G3 :| G | B F G B | B2 A D | F G F E | D3 A | B c d G/A/ | 
 B2 A A | B G A F | G3 ||  