Assemble a piece of music by merging the alphabetic representation of the predetermined musical pattern and the provided melodic theme.
X:1
L:1/4
M:4/4
K:G
['B A G', 'e d']  
X:1
L:1/4
M:4/4
K:G
 (3D E F | G F G B A G E D | G B d g e2 (3d e f | g f g d e d B G | A B A G E2 (3D E F | 
 G F G B A G E D | G B d g e2 (3d e f | g f g d e d B G | (3A B A G F G2 :| d | g f e g f e d f | 
 e d e f e d B2 | (3d e f g d e d B G | A B A G E2 (3D E F | G F G B A G E D | G B d g e2 (3d e f | 
 g f g d e d B G | (3A B A G F G3 :|  