There are provided a mixing apparatus that enables a user who is mixing and the like to be positively engaged in the performance of a musical composition at a low cost by simple operations, a method of controlling the same, and a mixing control program. A plurality of first audio data are input, and the input plurality of first audio data are mixed. A storage device stores a plurality of second audio data. A plurality of operating members are each disposed to be depressed and have a sensor for detecting the depression. At least one of the plurality of second audio data stored in the storage device is assigned, respectively, to at least one of the plurality of operating members. The second audio data is reproduced when the at least one of the plurality of operating members to which the second audio data is assigned is detected as being depressed. The second audio data reproduced by the reproducing device is input, and the input second audio data and the input first audio data are mixed.