A tine spring, also known as a tuning spring or tine coil, is a metal coil of wire that is inserted on to the tine of a note in a Rhodes piano. Its function is to finely adjust the tuning of a particular note.
Each tone bar assembly on a Rhodes piano has a tine spring. It is usually positioned towards the pickup end of the tine. Ideally it should avoid touching the damper or the hammer tip, but sometimes due to tuning that cannot be avoided. The coil is moved forwards or backwards to adjust the tuning. It achieves this by acting as a counterweight to the tone bar, moving the centre of mass by a slight amount, and therefore affecting the pitch of the note. To make the tuning sharp, the coil is moved away from the pickup. To make the tuning flat, the coil is moved towards the pickup. When tuning a Rhodes the coil only needs to be moved a very small amount to significantly affect the pitch. For more information on tuning a Rhodes piano see our post How Is A Rhodes Piano Tuned?
There are five different sizes of coil used in Rhodes pianos, with the thickest and largest being in the bass end, and the smallest in the treble end. The larger the coil, the greater the variation in tuning will be. When replacing a broken tine, changing the coil a size up or size down can be needed if the tine has not been cut to the correct length.
