It may not be clear to readers what this means. I suggest an additional note, after the 4th paragraph of Section 6, as follows:
Accessible means that the page maintains a reference to the object, or could obtain one from another object to which it has access (in this case from a Media Element). Therefore, the above requirement means that a <a>MediaKeySession</a> remains active and continues to receive events provided the page maintains a reference to the associated <a>MediaKeys</a> object or a Media Element to which it is attached. If that is not the case, the <a>MediaKeySession</a> could never be used and will not receive further events.
Additionally, this section uses the term "asynchronously" when it should say "in parallel".
The specification describes the MediaKeySession lifecycle in terms of whether it is "accessible", based on an original discussion and proposal here: https://www.w3.org/Bugs/Public/show_bug.cgi?id=24771
It may not be clear to readers what this means. I suggest an additional note, after the 4th paragraph of Section 6, as follows:
Additionally, this section uses the term "asynchronously" when it should say "in parallel".