Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:2/2
K:G
['G2 AD FGAF G2']  
X:1
L:1/8
M:2/2
K:G
"G" G2 BG"C" cG"G"BG |"D" AD D2"D" FGAF |"G" G2 BG"C" cG"G"BG |"D" Addc"G" BGGD | 
"G" G2 BG"C" cG"G"BG |"D" AD D2"D" FGAF |"G" G2 BG"C" cG"G"BG |"D" A2 dc"G" BG G2 || 
"G" g2 dg"G" Bgdg |"G" g2 dg"Am" eaaf |"G" g2 dg"G" BgdB |"Am" cAdc"G" BG G2 :|  