The 'tone' filter examples are both using calcBiquad(..); but one uses AudioFilterBiquad and other uses SGTL5000 PEQ filters. Had included code for volume level control optionally and decided to drop it from both.
Changed method for setting level/gains for left & right from 'item_left(..); item_right(..);' style to 'volume(left,right)' style instead.