What Is The Formula Device?

Also, this thread is a completely dead duck without this (thanks to kazakore from another thread ( Enabling The Formula Meta Device ) ):

<filterdevicechainclipboard doc_version="0">
  <devicecontainerslot type="SequencerTrackDeviceChain">
    <devices>
      <sequencertrackdevice type="SequencerTrackDevice">
        <isactive>true</isactive>
        <isselected>false</isselected>
        <selectedpresetname>Init</selectedpresetname>
        <selectedpresetismodified>false</selectedpresetismodified>
        <ismaximized>true</ismaximized>
        <customdevicename>Mixer</customdevicename>
        <panning>
          <value>0.5</value>
          <visualization>Device only</visualization>
        </panning>
        <volume>
          <value>1.0</value>
          <visualization>Device only</visualization>
        </volume>
        <surround>
          <value>0.0</value>
          <visualization>Device only</visualization>
        </surround>
        <postpanning>
          <value>0.5</value>
          <visualization>Device only</visualization>
        </postpanning>
        <postvolume>
          <value>1.0</value>
          <visualization>Device only</visualization>
        </postvolume>
        <smoothparameterchanges>true</smoothparameterchanges>
      </sequencertrackdevice>
      <formulametadevice type="FormulaMetaDevice">
        <isactive>true</isactive>
        <isselected>true</isselected>
        <selectedpresetname>Init</selectedpresetname>
        <selectedpresetismodified>true</selectedpresetismodified>
        <ismaximized>true</ismaximized>
        <formulaparagraphs>
          <formulaparagraph></formulaparagraph>
        </formulaparagraphs>
        <functionsparagraphs>
          <functionsparagraph></functionsparagraph>
        </functionsparagraphs>
        <inputnamea>A</inputnamea>
        <inputnameb>B</inputnameb>
        <inputnamec>C</inputnamec>
        <editorvisible>true</editorvisible>
        <panelvisible>1</panelvisible>
        <inputa>
          <value>0.0</value>
          <visualization>Device only</visualization>
        </inputa>
        <inputb>
          <value>0.0</value>
          <visualization>Device only</visualization>
        </inputb>
        <inputc>
          <value>0.0</value>
          <visualization>Device only</visualization>
        </inputc>
        <desttrack>
          <value>-1</value>
          <visualization>Device only</visualization>
        </desttrack>
        <desteffect>
          <value>-1</value>
          <visualization>Device only</visualization>
        </desteffect>
        <destparameter>
          <value>-1</value>
          <visualization>Device only</visualization>
        </destparameter>
      </formulametadevice>
    </devices>
  </devicecontainerslot>
</filterdevicechainclipboard>