Develop a musical composition based on the provided pattern of letters and incorporating the given motif within it.
X:1
L:1/8
M:4/4
K:C
['BEA Dec |[M:2/2][K:D]SOSOO .!fermata!PMTCO(Mec)', 'ABAF DFAF E2 (EB) AFAd BGBd cABc', 'fafd gfed cdef gfef gbag']  
X:1
L:1/8
M:4/4
K:C
 BEA Dec |[M:2/2][K:D]SOSOO .!fermata!PMTCO(Mec) |: AFdB ABAF | DFAF E2 (EB) | AFAd BGBd | 
 cABc dcdB | AFdB ABAF | DFAF E2 (EB) | AFAd BGBd | cABc defg || a2 (fd) fafd | gfed cdef | 
 gfef gbag | fgec defg | a2 (fd) fafd | gfed cdef | gfef gbag |1 faec dedB :|2 A3 c d2 |]  