Track Audio Language Requirement
April 1, 2019
Track Audio Language will soon be a requirement for all deliveries for Apple Music and iTunes. Use the <audio_language> tag in your metadata to denote the language of the lyrics on the song. iTunes Producer users can make this change by selecting a language from the “Language” pull-down menu in iTunes Producer.
See, Track Audio Language in iTunes Package Music Specification 5.3.6 for further information.