Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
Q:1/4=110
M:2/4
K:F
['FF{B} AG/F/', 'Ff (3gfg Gg']  
X:1
L:1/8
Q:1/4=110
M:2/4
K:F
 C | FF{B} AG/F/ | cA Af |{g} fe/f/{g} fe/f/ | cAAC | FF{B} AG/F/ | cAAf |{g} fe/f/ c/d/c/B/ | 
 AFF :: (3c/d/e/ | (3fef Ff | (3gfg Gg | (3fef (3gfg | af fc | (3fef Ff | (3gfg Gg | 
 f/g/a/f/ c/d/c/B/ | AFF :|  