A signal processing apparatus which is capable of reducing the occurrence of noise at editing points without the need to decode an encoded audio signal when editing the encoded audio signal. A recording/reproduction section reproduces an audio signal sequence including an audio signal encoded according to normalization information for controlling amplitude of the audio signal, and the normalization information. A normalization information converter changes the normalization information of the reproduced audio signal sequence. At least one of a first normalization information corresponding to a first encoded audio signal of a first audio signal sequence as the reproduced audio signal sequence and a second normalization information corresponding to a second encoded audio signal of a second audio signal sequence as the reproduced audio signal sequence are changed by the normalization information converter, such that the value of the first normalization information and the value of the second normalization information become equal.