Go to Options->Music & Sound Options.

Select any slider and move it to the left or right. (i.e., from 100% to Off). 

What happens is, the first time adjusting the sliders, there is initial lag, or jerkiness. You may also notice that while holding down the mouse button when adjusting the slider, other buttons will become highlighted if the mouse hovers over them, while the mouse button is held down for adjusting another slider.