srecord GainSoundSource(double gain, VF1<double[]> source) extends VF1<double[]> {
  public void get(double[] lr) {
    source.get(lr);
    if (isNaN(lr[0])) ret;
    for i over lr: 
      lr[i] *= gain;
  }
  
  void replaceSource(VF1<double[]> source) {
    this.source = source;
  }
}