Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:A
['eccc c2 BA', 'e2 cB', 'BBBa eccc c2 BA Bcef']  
X:1
L:1/8
M:4/4
K:A
 a | eccc c2 BA | Bcef ecca | eccc c2 BA | Bcac BBBa | eccc c2 BA | Bcef ecce | aefc e2 cB | 
 cefc AAA :| f | e2 cB ce f2- | fefa e2 cc | e2 cB ce f2 | ecBA BBBc | e2 cB ce f2- | fefa ecce | 
 aefc e2 cB | cefc AAA :| a | eccc ccBA | Bcef ecca | eccB ccBc- | ceac BBBa | eccc c2 BA | 
 Bcef ecca | aefc e2 cB | cefc AAAa | eccc cccc | ceef ecca | eccc Bccc | Bcac BBBa | eccc c2 BA | 
 Bcef ecce | aefc e2 cB | cefc AAA ||  