Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:3/4
K:G
['G2 GGGG G2 Tg4 bagfed Tc4 B2', 'A6 TB2 c2 d2 e3 dcB ABcBAG']  
X:1
L:1/8
M:3/4
K:G
 G2 GGGG | G2 Tg4 | bagfed | Tc4 B2 | A2 AAAA | AB c4 | Bd c2 B2 | A6 :: TB2 c2 d2 | e3 dcB | 
 ABcBAG | TF2 EF D2 | G2 GGGG | G2 gf g2 | (3ecA (3dBG (3cAF | G6 :|  