There is provided a mixing recorder which enables the user to readily produce music using overdubbing and/or other recording techniques while suppressing degradation of sound quality to the minimum and enables the user to easily find out his/her desired mixing result from a large number of mixing results obtained in the process of mixing. An audio signal is input, and a source file is read out from a memory card and an audio signal is reproduced based on the source file. The input audio signal and the reproduced audio signal are mixed into a mixed signal, which is then stored as a new source file in the memory card. The source file stored in advance in the memory card is backed up before the new source file is stored in the memory card, and in the back-up, the source file is automatically backed up by generating a file given a new name associated with a name of a source file to be backed up and having the same contents as the contents of the source file.