A driver computes a property's value from other properties via a function or Python expression

Drivers are Blender’s way to control a property’s value by a function or mathematical expression rather than by fixed keyframes. A driver takes zero, one, or more input values (from other properties or object transform channels), combines them with a preset function or a custom Python expression, and maps the result through an F-Curve to the driven property. For example, the rotation of one object can be controlled by the scale of another — the second object’s scale drives the first’s rotation. Drivers are the mechanism for making one parameter depend on another live and continuously, which is exactly what audio-reactive visuals need: an incoming analysis value (mapped in as a custom property) can drive scale, rotation, emission, or a Geometry Nodes input every frame, without hand-animating each keyframe.

Examples

Drive an object’s emission strength from a custom property that a script updates with an audio amplitude value; drive rotation from another object’s transform so the two stay linked.

Assessment

Explain what a driver does and give one example of one property driving another, then describe how a driver could make a visual parameter respond to an external (e.g. audio) value.