In addition to its common properties, the audio element has several properties of its own.
|duration||media||Identical to duration from the common properties, but with the addition that it can be set to media to make the element as long as the source audio clip.|
|source||null||The URL of an audio clip (an mp3) you want to insert. If it was uploaded using the template editor, it may also be its internal GUID.|
|trim_start||null||Trims the source audio clip to begin at the specified time (in seconds) rather than at the beginning of the audio file.|
|trim_duration||null||Trims the source audio clip so that it stops playing after the specified duration (in seconds) rather than at the end of the clip.|
|loop||false||When set to true, the audio clip starts over when it reaches the end. This property cannot be used in conjunction with the trim_start and trim_duration properties.|
|volume||100%||Adjusts the volume from 0% to 100%.|
|audio_fade_in||null||Fades in the volume for the specified duration (in seconds) at the beginning of the audio clip.|
|audio_fade_out||null||Fades out the volume for the specified duration (in seconds) at the end of the audio clip.|
Check out the template editor's documentation on the audio element as well.