首楞嚴義疏注經 6.280

6.280

解脫德也。如前觀音所陳三昧，所得殊勝，赴感不差，周遍皆應。十方者，十界也。擊鼓者，機動也。一時聞者，應不失也。此則應身無量，無感不應，故云圓真實。

This is the virtue of liberation. It corresponds to the samādhi previously set forth by Avalokiteśvara: the excellence attained responds to stimulus without fail, pervading everywhere in response. 'Ten directions' means the ten realms. 'Beating drums' means the faculties being activated. 'Hearing all at once' means the response never fails. This means his response bodies are limitless, responding to every stimulus without exception; hence it is called 'complete reality'.