According to a time-scale modification method or apparatus, wave segments each having a prescribed cutting length are sequentially cut from original digital signal waves stored in a waveform memory and are then spliced together by way of cross-fading, so it is possible to realize time-scale modification (i.e., compression or expansion with respect to time) in accordance with a designated time-scale modification factor. Herein, time-scale modification parameters such as a cross-fade duration, a search start time and a search end time are produced in response to the designated time-scale modification factor. In addition, a cutting start position is used for cutting a next wave segment following a present wave segment. The cutting start time is determined within a period of time between the search start time and search end time in such a way that it is placed to provide a best similarity between the wave segments having prescribed portions which are connected with each other by way of cross-fading. Specifically, a back-end portion of the present wave segment and a top portion of the next wave segment are smoothly connected together by way of the cross-fading, wherein they have the same cross-fade duration. The cross-fade duration is controlled to be longer as the time-scale modification factor becomes greater or smaller than "1". The cross-fading is actualized by a window function having different cross-fade coefficients, which are varied over a lapse of time and by which data of the prescribed portions of the wave segments are multiplied and mixed together.

A time-axis compression/expansion method and apparatus for multitrack signals is provided, which is capable of performing time-axis compression/expansion on a multitrack signal in such an appropriate manner as to prevent a degradation in the sound quality of a sound generated through a multichannel reproduction or a sound generated through reproduction of a musical tone signal obtained by mix-down. Positions of attacks of the rhythm track sound source signal of a plurality of track sound source signals are detected. Portions of the rhythm track sound source signal between the detected positions of attacks are subjected to a first time-axis compression/expansion process, and the other track sound source signals are subjected to a second time-axis compression/expansion process, based on the detected positions of attacks.

Distortion artifacts preceding a signal transient in an audio signal stream processed by a transform-based low-bit-rate audio coding system employing coding blocks are reduced by detecting a transient in the audio signal stream and shifting the temporal relationship of the transient with respect to the coding blocks such that the time duration of the distortion artifacts is reduced. The audio data is time scaled in such a way that the transients are temporally repositioned prior to quantization in a transform-based low-bit-rate audio encoder so as to reduce the amount of pre-noise in the decoded audio signal. Alternatively, or in addition, in a transform-based low-bit-rate audio coding system, a transient in the audio signal stream is detected and a portion of the distortion artifacts are time compressed such that the time duration of the distortion artifacts is reduced.