There is provided a portable mixing recorder which enables a user to readily produce music using overdubbing and/or other recording techniques while suppressing degradation of sound quality to the minimum without excessive concern for space restriction. An input analog audio signal is converted to a digital audio signal by an A/D converter section. A decoder reads out a compressed audio signal from an original source file stored in a memory card, and then extends the compressed audio signal to a digital audio signal. A mixing section mixes the digital audio signal obtained by the A/D conversion by the A/D converter section and the digital audio signal obtained by the extension by the decoder. An encoder compresses the digital audio signal obtained by the mixing by the mixing section to a compressed audio signal (mixed file). The mixed file obtained by the compression by the encoder is stored as a new source file in the memory card.