The Render Effect button allows you to render an audio effect without closing the Audio Mix tool. For example, if you change the level of a clip that contains a rendered audio dissolve, the effect becomes unrendered. You can use the Render Effect button to rerender the audio dissolves directly from the Audio Mix tool. Then, you can play the clip back immediately to hear the effect of the level change with the dissolve in place. For more information about rendering, see Rendering Effects.