Of course, the actual music does not really slow down, nor change in pitch, nor timing (unless stylus drag actually slows a turntable down!)..
But our perception of when the beat starts is affected by the arrival pattern in time of the first transients of a note. If the leading edge is sharp, not smeared in time, your brain will snap into recognising the start of something special. I am suggesting microseconds here! Get this right, and you'll likely find your foot tapping ...
... what smears out transients in time is poor driver alignment, cancellation between drivers around cross-over points, and interfering reflections from room surfaces. These are all reduced if your speakers behave like point sources.