The MiniDisc is suitable for recording and playback of audio and has a storage capacity of 290 MB in the standard version, and about 1 GB in the Hi-MD version. The high storage density is based on magneto-optical storage techniques. With the lossy compression Adaptive Transform Acoustic Coding( ATRAC) developed by Sony, a reduction factor of 4.83 is achieved and a high sound quality because the ATRAC process works with three frequency bands up to 21 kHz. MiniDisc can record about 60 to 74 minutes of audio and can be recorded as often as desired. The MiniDisc can only be played back in Sony devices such as the MiniDisc Walkman.