Significant pair of musical works, back-to-back with common ending (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

OPERA (a musical work performed on stage), then EVITA (a specific musical work) reversed (so that the two words are back-to-back), sharing the final A of both words (with common ending). As in “the operative word” = the one that carries the main point of what’s being said.