Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:F
['F3 G', 'cA GF']  
X:1
L:1/8
M:4/4
K:F
 F3 G A2 f2 | (cA) (GF) G2 (FD) | F3 G (AF) (Ac) | (dc) (dF) A2 f2- || f>g | ag/f/ gf/e/ fd cf | 
 cA GF G2 FD | f>gf>d cd fd | cA cF A2 f>g | ag/f/ gf/e/ fd cf | cA GF D2 f2 | cA GF (CD) (FG) | 
 A3 G A2 f2 ||  