The purpose of this study is to clarify how learners' attitudes, learning, and trial-and-error change when unusual tasks are added to a university student's opera production. The research method was to analyze the learners' descriptions after the opera performance. The target opera performances were (1) a regular opera performance, (2) an outdoor opera performance, (3) a double-cast opera performance, and (4) an opera performance in collaboration with another group. The following results were obtained by comparing (1) regular opera performances and other performances. (2) In the outdoor opera performance, the learners were anxious about performing in a different venue than usual, but there was not much trial-and-error. (3) In the double-cast opera performance, the learners made some trial-and-error attempts to improve their performance and acting skills. The double-cast performances did not have much impact on the students. (4) In opera performances with other groups, learners were influenced by the other groups, but did not make much trial-and-error. In opera productions, it is effective to give learners special challenges, but it is more important for the instructor to encourage them afterwards.