Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:6/8
K:G
['First Clan March of', 'ABd edB AGD GBA B2 A', 'dBd egB A2 G', 'e2 e', 'dfa dfa']  
X:1
L:1/8
M:6/8
K:G
"^The First Clan March of the O'Sullivans" D |: GBA ABd | edB AGD | GBA B2 A | AGE GED | G2 B ABd | 
 edB AGD | GBA B2 A |1 AGG G2 D :|2 AGG G2 g |: e2 g e2 g | ege edB | d2 d dBd | egB A2 G | 
 c2 c dBd | egB A2 G | GBA B2 A |1 AGG G2 g :|2 AGG G2 D || 
[K:D]"^Highland March from Oscar & Malvina" d3 d2 e | dcB ABc | dcB AGF | GEF GFE | e2 e e2 e | 
 fed eag | fed dAB |1 def e3 :|2 def e2 f |: fed eAA | fed e2 a | gfe fBB | gfe fBB | fed e2 A | 
 fed eag | fed dAB |1 def e2 f :|2 def e2 e | dfa dfa | a2 a afd | egb egb | egb bge | dfa dfa | 
 dfa a2 g | fed dAB | def e3 || d2 a dfa | a3 afd | egb e2 b | egb bge | dfa dfa | dfa a2 g | 
 fed dAB | def e3 ||  