Answer: Igor Stravinsky's L'Histoire du soldat, which instead uses a speaker and 3 mimed acting roles.
Rick Bogart's Opera Glass at the Stanford University site contains a very useful list of operas for 6 or fewer characters. In this list are a number of solutions for various situations that often arise in smaller college programs and companies where the number of available voice types can tend to be skewed. Here are some possibilities:
- Four sopranos and a tenor--Mozart's Ascanio in Alba
- One-woman opera for mezzo soprano--Lee Hoiby's Bon Appetit
- One mezzo, two tenors and three baritones or basses--two choices, Stravinsiy's Oedipus Rex or Massenet's La Navarraise