Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:6/8
K:Gmin
['B>BB B2 c B>AA A2 A (G2', 'b2 g']  
X:1
L:1/8
M:6/8
K:Gmin
 B>BB B2 c | B>AA A2 A | (G2 d) (d2 c) | B2 G A2 z | B>BB B2 c | B>AA A2 A | (G2 d) (d2 c) | 
 (B2 A) G2 || a | b2 g g>^fg | b2 g g>^fg | b2 g d>cB | c2 c c>BA | B>BB B2 c | B>AA A2 A | 
 (G2 d) (d2 c) | (B2 A) G2 z ||  