Score number (4)
(Other definitions for twenty that I've seen before include "One score" , "Dozen plus eight" , "Cardinal" , "Score, XX" , "Figure" .)
(Other definitions for aria that I've seen before include "Puccini item" , "Operatic number" , "Song from an opera (4)" , "Operatic tune" , "Vocal solo in a cantata etc" .)