Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:2/4
K:G
['FA dF .G2 de cA', 'g2 z']  
X:1
L:1/8
M:2/4
K:G
 D |:"D7" FA dF |"G" .G2 !>!g2 |"D7" de cA |{/A}"G" GF GD |"D7" FA dF |"G" .G2 !>!g2 |"D7" de cA |1 
"G" G2 z D :|2"G" G2 z a |:[K:D]"D" fb/a/ ^ga |"A7" e'3 f' |{/e'}"D" d'c' d'a |"A7" e'3 f' | 
{/e'}"D" d'c' d'^d' |"G" e'g bd |"A7" dc Bc |1"D" d2 z a :|2"D" d2 z d |:[K:G]"D7" a3 a/g/ | 
 ff ga |"G" b3 b/a/ | gg gb |"D7" c'e' d'c' |{/c'}"G" b^a bg |{/b}"D7" a^g af |1"G" g2 z d :|2 
"G" g2 z B |:"Em" gf/e/ ^de |"B7" fB ^c^d |{/f}"Em" e^d eg |"B7" b2 z b |"G" b>g d>b | 
"Am" a>e c>a |"D7" fA df |1"G" g2 z B :|2"G" g2 z2 |]  