manual/include/balance-control.html

<p>
  For stereo tracks, you can now switch between the default stereo panner
  and a traditional <dfn>balance control</dfn> by right-clicking on the
  panner widget.
</p>
<img class="left" src="/images/stereo-balance.png" alt="Stereo Balance
control"/>
<p>
  When the balance is centered, the incoming signals will be unaffected.
  Moving it to one side will linearly attenuate the signal of the opposite
  side.
</p>
<p class="note">
  While the balance control is considerably less flexible than the stereo
  panner, it works with arbitrary content without danger of introducing
  comb filter artefacts.
</p>