Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
M:2/2
K:D
['d2 fd']  
X:1
L:1/8
M:2/2
K:D
"Bm" fBBA FEFB |"D" A2 FB"A" ABde |"Bm" fBBA FEFA |"A" (3Bcd cA"Bm" B2 Be | fBBA FEFB | 
"D" A2 FB"A" ABde |"Bm" fbaf"A" egfe |1"D" dBAF"Bm" B3 e :|2"D" dBAF"Bm" B3 A |:"D" d2 fd Adfa | 
"Bm" bfaf"A" egfe |"D" d2 fd Adfb |"Bm" bfaf"A" egfe |"D" d2 fd Adfa |"Bm" bfaf"Em" e2 de | 
"Bm" fBBA FEFA |1"A" (3Bcd cA"Bm" B3 A :|2"A" (3Bcd cA"Bm" B3 z |]  