This is a quick tutorial on merging mp3 files together. Like many seemingly trivial computing tasks that one would imagine are easy to perform in the year 2021 this is remarkably not easy to do. This is the fastest route I discovered and I hope it's helpful.
Open terminal or iTerm and run
brew install -v mp3wrap id3lib ffmpeg to install all the required packages
mp3wrap temp.mp3 combinedme1.mp3 combineme2.mp3 ... (... can include as many mp3 files as you need to combine)
Next run ffmpeg to copy the mp3s together into a single file
ffmpeg -i temp.mp3 -acodec copy combined.mp3
Now copy your tags over from the first mp3 file
id3cp combineme1.mp3 combined.mp3
Delete the temporary files
Now you have a neatly combined
combined.mp3. If you wish to edit the metadata of the mp3 I recommend using Squeed.