The performance of tape recording is greatly affected by the width of the tracks used to record a signal, and the speed of the tape. The wider and faster the better, but of course this uses more tape. These factors lead directly to improved frequency response, signal-to-noise ratio, and high-frequency distortion figures. Tape can accommodate multiple parallel tracks, allowing not just stereo recordings, but multi-track recordings too. This gives the producer of the final edit much greater flexibility, allowing a performance to be remixed long after the performance was originally recorded. This innovation was a great driving force behind the explosion of popular music in the late 1950s and 1960s. The first multi-tracking recorders had two, three, or four tracks, then eight, sixteen, and twenty-four, and so on. It was discovered early on that new special effects were possible, such as phasing and flanging, delays and echo by re-directing the signal through one or more additional tape machines, while recording the composite result to another. These innovations appeared on pop recordings shortly after multi-tracking recorders were introduced, although, Les Paul had been using tape echo and speed-manipulation effects on his single-track recordings from the 1940s and '50s.