A session terminal apparatus constitutes a network session system together with another session terminal apparatus. In the session terminal apparatus, a back performance instruction part instructs reproduction of back performance information. A back performance control part transmits the back performance information, when the reproduction thereof is instructed by the back performance instruction part, to another session terminal apparatus, and controls a performance reproduction part to start reproducing the back performance information when a monitor delay time corresponding to a communication delay time between the session terminal apparatus and another session terminal apparatus has elapsed after the reproduction of the back performance information was instructed.