Reference Manual - 1.1.1
IFusionSound   SetLocalVolume

Set local volume level.

SetLocalVolume (
  IFusionSound   * thiz,
  float   level
);

Set the local volume level (i.e. that applies to the playbacks created by the current process).
The level is a linear factor ranging from 0.0f to 1.0f.

See also GetLocalVolume().