Formulate a musical piece by utilizing the specified motif and alphabet-based structure.
X:1
L:1/8
M:4/4
K:D
['afaf gbgb afaf', 'dafd caec']  
X:1
L:1/8
M:4/4
K:D
 dfaf dcBA | B2 G2 G4 | dbba gfed | c2 A2 A2 fg | afaf gbgb | afaf gbgb | afaf gbag | f2 d2 d2 || 
 A2 | dfaf dcBA | GdBd GdBd | cgba gfed | caea caea | dafd caec | dafd caec | dbag fedc | 
 d2 dd d2 ||  