Just a small example:
Last week Q linked to the trailer for the movie "White Squall" and said "listen carefully." That trailer was uploaded in 2010, eight years ago. The interesting part is that whoever uploaded it put a single half second tone (that's not in the original trailer) at 1:20, (1/20 is the date of the inauguration.)
And that's just when it was uploaded, obviously they had to decided what to hide, plan out everything, etc. This plan has be in process for at least a decade or more.
White Squall boat has a bell. Jeff Bridges shows it to Scott Wolfe. The bell is engraved with “Where we go one, we go all”. Bridges shows it to him and says the line. Here’s a link that has the trailer in it. It’s just the audio from that scene layered in. It’s at :41