Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:2/2
K:A
['AG FGAB A2 F2 E2 C2- C2', 'AB c2']  
X:1
L:1/8
M:2/2
K:A
|: AG | FGAB A2 F2 | E2 C2- C2 A2 | B4 B3 A | EF A2 A2 AG | FGAB A2 F2 | E2 C2- C2 E2 | 
 EF E2 C3 B, | B,2 A,2- A,2 :: AB | c2 cB A2 AB | c2 e2- e2 e2- | e2 ef e2 ec | B2 A2- A2 AB | 
 c2 cB A2 AB | cd e2 a2- ag | f2 g2 a3 f | e2 c2- c2 e2 | ef e2 c3 B | B2 A2- A2 :|  