CAP
From Just Solve the File Format Problem
The Capella notation software was one of the first music notation softwares to be released for Windows.[1] Currently uses the open CapXML format, but used a proprietary binary format previously.
Format Information
CAP version 3 (2000) files begin with the bytes 636170332D763A - ASCII "cap3-v:" with the next byte indicating version.[2] The developer package contains information on the older binary format.[3]
CAP version 2 is explained in developer package and here
