Assertion: contralto's role | /r/CapableOf | perform by mezzo sopranos
Facets:
value: often
type: TEMPORAL
Source sentences:
text: Roles written for contralto and often performed by mezzo sopranos include Azucena, Il Tovatore and Maddalena, Rigoletto, Verdi; Klymenestra, Elektra, Richard Strauss; Olga, Eugene Onegin, Tchaikovsky.