Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:6/8
K:D
["ua e'3 d'c'b a3 abc' d'3 d'af", 'aaa aaa']  
X:1
L:1/8
M:6/8
K:D
 ua | e'3 d'c'b | a3 abc' | d'3 d'af | dAF D2 z | e3 dcB | A3 Ace | a3 gfe | d2 z vd2 z || 
 vf2 z ug2 z | a3- a2 d | e3- efe | d3- d z uA | vf2 z ug2 z | a3- a2 f | e3 d'c'b | 
 aa/a/a a(.a.a) | aaa aaa | aaa aaa | aaa aaa | aaa [aA] z uA | [ge]3 [fd]3 | [eA]3 [gA][fA][eA] | 
 [fAD]3 fed | eAB cde | vf2 z ug2 z | va3- a2 d | e3- efe | d3- d2 uA | vf2 z ug2 z | a3- a2 d' | 
 c'ba gfe | d2 z vd'2"_D.C" |]  