Three short lines capture a small, strange moment: a radio broadcast goes silent. "Dead air" is the term for that unplanned gap when nothing is playing, and the poem begins right in the middle of it. The speaker was presumably listening to an opera, and now there is only emptiness where the music should be.
The turn comes in the last line, "out of time." It works in two ways. The broadcast has lost its timing, since the sound has dropped out of its schedule. But the speaker is out of time too, and the phrase can suggest being out of step, out of sync, or even running short of time. The word "both" links the speaker and the opera as equals, as if they share the same stalled condition.
The mood is quiet, a little lonely, and faintly wry. Nothing dramatic happens, yet the pause makes the speaker feel suspended and slightly disconnected from the world the music came from.