How to use chroma key if subject is wearing the same color?

Hello, everyone. I have been working on a meme video for awhile, which includes this video. In my video I edited it so that the laugher matches over the melody of the song that i am working with. Along with that, I have two tracks below that, which have clips that are mixed to the song as well. I would like the clips on the two tracks to show in the two vertical bars of the video, but because the guy is wearing a black sweatshirt, I am not sure what to do. Thank you for your time, and if you have further questions, please ask them below.

You can use the “Crop: Rectangle” filter to remove the black bars. And to show the track below, you set the alpha channel in the padding colour to zero.

But the black bars change size during the duration of the clip. So, how would I do that?

You use keyframes, which you can enable by pressing on the stop watch besides the position and size setting. Afterwards, you only have to adjust the rectangle every time the bars change in size.