A tone bar spring is a metal spring that is inserted between a tone bar and the harp of a Rhodes piano. Its function is to keep the tine and tone bar under tension so they remain in position for the hammer to strike the tine and generate a tone. There are two springs in each tone bar assembly.
The tone bar spring works alongside the tone bar screw, and the tone bar grommet. Therefore there are two of these per tone bar along with a washer that sits between the head of the screw and the grommet. The screws anchors the tone bar assembly to the harp, and the grommets helps remove the vibration of the tone bar transferring to the harp. The function of this is to improve sustain.
Without the springs, the tone bar would be fixed to the harp without any flexibility, causing there to be no sustain of the note. In a sense, because of the springs the tone bar ‘floats’ above the harp. Since the tone bar assembly acts as a kind of tuning fork, with vibrations between the two ‘forks’ sustaining the tone; any interference would cause this tone to stop. By having the tone bar assembly float’, the hammer can strike the tine and the vibration can be uninterrupted. This allows for a longer decay of the tone, hence why the springs are there.
There are three different types of spring used for Rhodes pianos, these are for the bass, mid, and treble sections. These roughly correspond with the harp support sections, but can vary depending on year of production and (if restored) the quality of restoration.
To improve sustain of notes, usually replacement of the springs is not needed. However if replacing the tone bar screws and grommets, it can be a good time to replace the springs if they are particularly worn.
In the bottom end of a Rhodes, the tines can vibrate uncontrollably causing them to hit their neighbours or the tone bar. Usually tines should vibrate up and down but sometimes in the very low end they will form a figure-of-eight pattern. This is because the length allows inconsistencies in the tine to be exaggerated. Replacing the front springs with tine stabiliser springs can help in the reduction of this motion. This is a much thicker spring which reduces movement of the tine.
