Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
M:4/4
K:G
['DGBG dGBG', 'g2 gf gbag']  
X:1
L:1/8
M:4/4
K:G
 DGBG dGBG | DFAF cFAF | DGBG dGBG | BdcA BGGE | DGBG dGBG | DFAF cFAF | DGBG dGBG | BdcA BGGd || 
 g2 gf gbag | fdde fgaf | g2 gf gbag | fdcA BGGd | g2 gf gbag | fdde fgaf | g2 gf gbag | 
 fdcA BGGF ||  