Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:6/8
K:Gdor
['BAG FDC DGG', 'BGd BGd BAB dcB', 'bag c=ff c=ff cBc ag=f dgg dgg']  
X:1
L:1/8
M:6/8
K:Gdor
 A | BAG FDC | DGG DGG | BAG ABc | d^cd gd=c | BAG FDC | DGG GAB | AGF DCA,- | A,G,G, G,2 :: A | 
 BGd BGd | BAB dcB | AFc fcB | AFA cBA | BGd BGd | BAB dcB |1 AFA cBc | AG^F G2 :|2 AGF DCA,- | 
 A,G,G, G,2 |:[K:G] B | dgg dgg | gfg bag | c=ff c=ff | cBc ag=f | dgg dgg | gfg bag | afd cAF | 
 AGF G2 :|  