code: function _createBiquadFilter (defaults) {
      return function (context, opts) {
          if (audioContext) {
              opts = context;
              context = audioContext;
          }
          opts = assign(opts, defaults);
  
          var filter = context.createBiquadFilter();
  
          Object.keys(opts).forEach(function (option) {
              if (option !== 'type') {
                  filter[option].value = opts[option];
              } else {
                  filter.type = opts[option];
              }
          });
  
          return filter;
      };
  }
docs: Thin biquad filter creation wrapper.
  @param  {Object} defaults Default options (usually just type)
  @api private