Variable area

A single unilateral variable area soundtrack.

A dual unilateral variable area soundtrack.

A single bilateral variable area soundtrack.

A dual bilateral variable area soundtrack.

Variable area is type of optical soundtrack. It should be differentiated from a variable density track, though the same equipment can be used for reading and playback of either type of track. Variable area tracks may consist of a single, double, or multiple tracks, and the tracks can be unilateral or bilateral.