What is tracker bars?

A tracker bar is a long bar with a series of holes or slots in it that allow for the attachment of tracker pins. These pins are used in mechanical musical instruments, such as player pianos, to control the playing of notes via a pneumatic system.

The tracker bar essentially acts as the control center for the music, with each pin corresponding to a specific note or chord. When air is forced through the tracker bar, it activates the corresponding pneumatic valve and causes the note to be played.

Tracker bars are typically made of wood or metal and can vary in length depending on the size of the musical instrument. Some bars are stationary while others are movable, allowing for adjustments to the playing mechanism.

Today, tracker bars are still used in some modern reproducing pianos and other mechanical musical instruments. However, electronic systems have largely replaced the need for traditional tracker bars in most digital and electronic instruments.