Develop a musical composition based on the provided pattern of letters and incorporating the given motif within it.
X:1
L:1/4
M:3/2
K:Bmix
['f B', 'B b2 a2 g2 a f- f', 'B d', 'b d']  
X:1
L:1/4
M:3/2
K:Bmix
|: B/c/d/e/ f B f B | A c- c e d c | B/c/d/e/ f B d B | F B- B d c B :: b2 a2 g2 | a f- f a g f | 
 e2 d2 c2 | d B- B d c B :: B/c/d/e/ f B d B | A c c e d c | B/c/d/e/ f B d B | F B B d c B :: 
 b2 a2 g b | a f f a g f | e b d b c b | d B B d c B :|  