@Polly Ticks
Have an honest question for you. Is the "Tomahawk Chop" chant now piped in through the sound system?
...because I never see the fans doing "The Chop" while it's being 'chanted'. 
@DCPatriot It's evolved over the years. For awhile, a guy banging on a huge timpani drum would be displayed on the Jumbotron to start it, then they would play the music through the sound system. Most recently up until 2019 (not counting last year because of no fans), they started it with whistles, then drumbeats, and then trumpets came in for the melody of it, all through the sound system.
As of this year, they quit doing the whistles and the trumpets/melody, and they only do the drumbeats on the sound system. The fans supply the rest. And the fans start their own chant here and there, without the drumbeat prompts.
Edited to add:
During a pitching change for the opposing team during a late inning, they also turn the lights down and the fans turn on their cell phone lights for the Chop.