Construct a musical piece that contains the provided motif and abides by the prescribed alphabetical scheme.
X:1
L:1/4
Q:3/4=90
M:6/4
K:Bb
['A B c', 'f g']  
X:1
L:1/4
Q:3/4=90
M:6/4
K:Bb
 D | (D E) B (B c) d | B3 F2 A | B c d d e f | d3 B2 c | d e f f e d | g3 G2 A | B c d d c B | 
 f3 F2 G | A B c c2 A | F3- F2 G | A B c c2 =e | f3- f2 || c | c3/2 d/ c c2 d | e3- e2 f | 
 g3/2 _a/ g f2 e | d3- d2 e | f3/2 g/ f e2 d | c3 d e f | g f e d c B | A3 F2 f | g a b a2 b | 
 b3- b2 c | d3/2 e/ f c2 B | B3- B2 |]  