I've not come across this yet and I really want to put it out there.
Now. We all assumed it's a call back to A Nightingale Sang in Berkeley Square. And I do think it still is (and why that song plays later).
However. I think there's more to the use of Nightingales than that.
There is a certain bit of literature out there, a very RELEVANT bit of literature actually, that uses Nightingales or, more specifically, the lack thereof, as a warning.
A bit of literature that both of them are probably quite familiar with as they canonically have attended this particular bard's performances.
The most well known literary star-crossed lovers.
Act 3, scene 5. Dawn is approaching after the (secretly) newly wed lovers have spent the night together.
Romeo must leave Juliet's room and get out of dodge before daybreak or risk being killed. Juliet, desperate for more time together, tries to convince him it is not yet morning and he should stay with her a bit longer.
Juliet tries to convince him the birdsong is that of the nightingale, a night-bird, and that they still have time to be together. Romeo replies that it is "no nightingale", but a lark, a bird of the morning, and that he must "be gone and live, or stay and die".
They tarry a bit longer as the scene continues until Juliet realizes the actual danger of him staying with her, and urges him to go. He does, but first :
Romeo: "Farewell, farewell! One kiss, and I'll descend!"
Now, i am a die hard believer that there was more going on in that last 15 than meets the eye, and I eventually plan to post about that, as well. The possibility that there was some non verbal communication going on between the lines. I am also very solidly of the belief that the Metatron story we (and Crowley) heard from Aziraphale was that of an Unreliable Narrator. Something was said or implied in that conversation that we don't know about. Something Not Good.
But, the No Nightingales line, which at first seemed like just a heavy hitting angst-hammer and call back to the end of s1, on rewatches seems...odd. A bit 4th wall, even.
Unless...there was a different intent with the use of the phrase. Specifically 'Listen. No Nightingales.'
And then we get the Nightingale song playing in the Bentley right after Aziraphale gets in that lift.
We know that Satan, other demons, and Crowley himself can speak through the radio.
And we know from s1 (Aziraphale's escape back to Earth when discorporated and his possession of Mdm. Tracy) that if demons can do something...angels can, too.
The song playing right then, I believe, was Aziraphale's attempt at comfort.
