In Trident the components of an <audio> element (play/pause, volume control, etc) can be tabbed through as well - these TABs are propagated to the document as regular KeyEvents. Gecko and Trident allow controlling the <audio> element by keyboard (left/right to seek, space to toggle playback, up/down to control volume) - these interactions are propagated to the document as regular KeyEvents. Blink allows neither.