The usual orchestral pedal harp has 7 strings per octave, tuned to a diatonic scale. 7 foot pedals each actuate semitone fretting mechanisms on all octave repetitions of one note of the octave.
The modern setup uses a pedal with 3 positions. The central position gives the natural note; the upper position
is flat and the lower position is sharp. The pedals are spring loaded into the upper position, and there are two notches to allow them to be set in the middle or lower position.
The semitone mechanism is some kind of pincer (most often a rotating 2-tined fork) than pinches the string at a preset point, sharpening it by exactly one semitone.
The proposed mechanism replaces the pincer with a sliding metal roller that moves up and down the string. As usual, all the rollers for octave repetitions of one note of the octave are mechanically connected together to one foot pedal.
Pressing the pedal down will slide the note sharp by any amount (according to the amount the pedal is depressed), up to a whole semitone. Lifting the pedal with the toe similarly flattens the note. Notches are provided in all three positions allowing the pedal to be latched in the flat, sharp, or natural position.
Each pedal is spring loaded as in the usual setup. Because players may not wish to have to lift the pedal with their toe beneath it, an 8th pedal moves the spring loading mechanism to allow the other 7 pedals to be spring loaded to either the centre position, or the top position, as the player prefers. This 8th pedal has notches at the top and the bottom of its travel. Needless to say, this 8th pedal can also be used in 'sliding mode', simultaneously bending every string on the harp, or a selection of them, depending if the other pedals have been placed in a notch or not.