CVU file is a CVSD Unfiltered Audio. Continuously Variable Slope Delta modulation (unfiltered) is an alternative handler for CVSD that is unfiltered but can be used with any bit-rate.
Ogg is a free open video format file which is designed to provide efficient streaming and manipulation of high quality digital multimedia. The Ogg file is similar to an MP3 file, but has better sound quality than an MP3 file of same size. It can include song metadata, such as artist information and track data, and is supported by many media players and some portable music players.