Assemble a piece of music by merging the alphabetic representation of the predetermined musical pattern and the provided melodic theme.
X:1
L:1/8
M:4/4
K:G
['GBAG E2', 'B2 B2']  
X:1
L:1/8
M:4/4
K:G
|: G2 GBAG E2 | G2 GB e2 d2 | g2 ge dcBA | GBAG E2 D2 | G2 GBAG E2 | G2 GB e2 d2 | g2 ge dcBA | 
 GBAG E2 D2 :: B2 B2 A2 GA | B2 B2 e2 d2 | B2 B2 A2 GA | BAGE D2 z2 | B2 B2 A2 GA | B2 B2 e2 d2 | 
 gfge dcBA | GBAG G2 G2 G2 :|  