A system and a corresponding method for temporal modification of audio signals, to increase or reduce the playback rates of an audio and/or a video file in a client-server environment. The system and method improve the efficiency of serving streaming media to a client so that the client can select an arbitrary time-speedup factor. The speedup system performs many of the pre-calculations once, at the server, so that the bandwidth needs are reduced and the client's computational load is minimized. The final time-scale-modification can be either done completely on the server, thus reducing the client's needs, or partly on the client's computer to minimize latency, and to reduce on-the-fly computational load from the server that serves multiple clients concurrently.