Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:2/4
K:F
['A cF GA Bd GA', 'c6 B2 e3 B d6']  
X:1
L:1/8
M:2/4
K:F
 A | cF GA | Bd GA | Bc df | c3 A | cF GA | Bd GA | cB AG | F2 z G | GG =B>G | cG cc | =BG de | 
 c2 z G | GG =BG | cG cc | =BG de | c2 _B ||[M:3/4] A2 d3 A | c6 | B2 e3 B | d6 | e4 B2 | e4 B2 | 
 d4 A2 | c6 | B2 e3 B | d6 | c3 c c2 | d3 d e2 | f6- | f2 z2 z2 ||  