As the current passing through the speaker’s coil changes, the speaker cone moves back and forth toward or away from the speaker’s permanent magnet. This moving cone pushes or pulls on the air, creating compressions and rarefactions that propagate through the air as sound.
During the silent passages of the music, the amplifier does not vary the amount of current passing through the speaker so that the speaker doesn’t move and doesn’t produce sound. To conserve energy and to avoid heating up the speaker, a good amplifier doesn’t send any current through the speaker during a quiet passage. Whether or not the amplifier actually consumes power during the quiet passage depends on the exact design of the amplifier. Some stereo experts claim that they can hear the differences between amplifiers the do or do not consume power with their output transistors during the quiet times and claim that the power wasting amplifiers sound better.