Completely stuck on three (usually not) and one explanation.
9A Magic headline - an adaptation from Puccini (3,6,6) C?E ?E?I?A ?A?I?A. Looks like an anag of 'magic headline an'.
27A. Festival choice includes Schubert overture (6) ?E?A??
20D Eucalyptus in pot starts to reach amazing heights(6) ?A?R??
13D. Point to essential part a serpent-nymph had in wedding hymns (11) EPITHALAMIA.
PS. The final A is my 27A 'A'