code: function logarithmic(length, base, rotation) {
      var curve = new Float32Array(length),
          index,
          x = 0,
          i;
  
      for (i = 0; i < length; i++) {
          //index for the curve array.
          index = rotation > 0 ? i : length - 1 - i;
  
          x = i / length;
          curve[index] = Math.log(1 + base * x) / Math.log(1 + base);
      }
  
      return curve;
  }
docs: creating a curve to simulate a logarithmic curve with setValueCurveAtTime.