OptionalissuerThe issuer of this event, as passed into the according API method. 'api' by default if no issuer was specified.
The volume before the event has been triggered
The new selected volume
The time at which this event was fired
Event type, e.g. 'play'
Events which can be triggered by user interaction as well as internally. The issuer is to determine whether this was triggered internally ('api') or by the UI ('ui')