Audio cassette
Type III - Ferrochrome - Type III tapes are a hybrid of Types I and II. They consist of a layer of ferric tape for strong bass, and a layer of chromium dioxide tape for strong treble. Type III tapes are no longer made and were never very popular because the ideal bias settings for CrO2 and ferric tape are different, so the person recording the tape is forced to choose a bias setting that is not ideal. Many tape recorders do not have a setting for them. On decks without a Type III setting, they should be recorded as a Type I.