Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:2/4
K:G
['G A']  
X:1
L:1/8
M:2/4
K:G
 A E D2 | F G A d | A G F E | D4 | A E D2 | F G A d | A4 | A E D2 | D2 G A | d2 A/ G/ A/ d/ | 
 A G F E | D3 D | G A F E | D4 |]  