Abstract: A mechanism including a sustaining bar (112) directly engaging a row of damper supports (104); and a harmonic bar directly engaging a row of escapements (13) each of which is combined with one of the damper supports. Both bars (111, 112) are actuated by a common pedal (1) to which they are connected by a linkage system (18, 20, 5) linking the movement of the harmonic bar (111) to that of the sustaining bar (112) so that when the pedal is depressed beyond a so-called "harmonic" position in which the pedal is half-depressed, the sustaining function is applied to all the notes whose keys are depressed, and once the pedal has been fully depressed and is therefore in a so-called "forte" position, then very slightly released, all the escapements are in engagement with the harmonic bar.