Develop a musical piece that combines the given theme and letter-structured outline.
X:1
L:1/8
M:3/4
K:G
['_B2 G2']  
X:1
L:1/8
M:3/4
K:G
 GG _B2 G2 | AA d2 d2 | cc _B2 G2 | =F4 FG | GG _B2 G2 | A2 d2 d2 | _BGBAGF | G6 |]  