HTMLAudioElement.msAudioCategory
Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
  The msAudioCategory property of the HTML <audio> element, is a read/write proprietary attribute, specific to Internet Explorer and Microsoft Edge.
 msAudioCategory specifies the purpose of the audio or video media, such as background audio or alerts.
 
Syntax
<audio controls="controls" msaudiocategory="BackgroundCapableMedia">  </audio>
  The msAudioCategory property offers a variety of values that can enhance the behavior of your audio-aware app.
 Note that you must set the msAudioCategory before setting the src property in code.
 
Value
Include a description of the property's value, including data type and what it represents.
  If msAudioDeviceType is not explicitly set, msAudioDeviceType will be set to Communications.
 For hardware audio offload to be automatically applied, the audio category must be set to ForegroundOnlyMedia or BackgroundCapableMedia. Hardware audio offload optimizes audio rendering which can improve functionality and battery life.
 
Example
<audio msAudioCategory="BackgroundCapableMedia" controls="controls">
  <source src="song.mp3"/>
</audio>