Audio Mixer
A master bus and one strip per audio plate in the scene.
How the final gain is worked out.
Gain and mute are read straight from the node's media settings, so the strip and the component's own inspector fields are the same value — there is no second, hidden level.
A channel is audible only when it is not muted, not silenced by another channel's solo, and actually has a source. The master bus meter lights when at least one channel is live and the master is not muted.