Develop a musical piece employing the provided motif and an alphabet-based structure.
X:1
L:1/8
M:4/4
K:Gmix
['', 'AF cA BG']  
X:1
L:1/8
M:4/4
K:Gmix
 c2 |: BG DG BG dB | AF CF AF cA | BG DG BG dB |1 AF cA BG Gc :|2 AF cA BG GB ||  