Start of CAT infiltration

 is a track in Xenosaga Episode III. It has not been released on any soundtrack or sound selection and not much is known about this track.

It plays in the cutscene when the Elsa makes its way to the Yuriev-controlled Durandal.

 is a version of start of CAT infiltration without the rhythm guitar or main string melody. Like the original, it has not been released on any soundtrack or sound selection and not much is known about this track.

This track plays as the area music on the Elsa in the following instances:
 * When the party is on Rennes-le-Château.
 * After the first Voyager fight.
 * Immediately at the start of Disc 2 before the party leaves for Merkabah.
 * After leaving Merkabah, before the party leaves for the.
 * Before and while the Elsa is inside Abel's Ark.

It also plays in the following cutscenes:
 * The party plans their break-in to the C.A.T. Testing Grounds in the Mobius Hotel.
 * Allen briefs the party on the route to where KOS-MOS is outside the C.A.T. Testing Grounds.