Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:G
['G>d B>G F>c A>F (3GFG B>G D2', 'A>G F>A']  
X:1
L:1/8
M:4/4
K:G
 (3DEF | G>d B>G F>c A>F | (3GFG B>G D2 G>F | E>G A>B c>B A>G | F>d (3d^cd e>d =c>A | 
 G>d B>G F>c A>F | (3GFG B>G D2 G>F | E>e d>c B>A G>F | A2 G2 G2 :: A>G | F>A d>^c d>B A>G | 
 F>A d>^c d>f e>d | ^c>d e>f (3gfe c>e | d>^c d>e d2 =c2 | B>c B>A ^G>B e2 | A>B A>G F>A d2 | 
 e>g f>e (3ded (3cBA | G>g d>B G2 :|  