A pop that I can't get rid of?

I’m trying to arrange two tracks so that as soon as one ends, the other begins. The problem is, I’ve got a pop at the very end of the first track, and when I delete it, it just comes right back. I tried silencing it instead of removing it, and it had no effect. Here is what the pop looks like in spectrogram mode. What do I do? Nothing seems to affect this invincible pop.

You will get a pop if the waveform stops abruptly above or below the centre line. A common case is when the audio suffers from “DC offset” (see: http://manual.audacityteam.org/man/dc_offset.html). If DC offset is present, it should be fixed before you do anything else.

Try applying a short fade-out to the end of the track.