I'm looking for a way to insert a custom sound at a given second into an MP3 track. I'd like to be able to do this without GUI tools so I can invoke it from a bash script, and I'd like this sound to be layered over the regular track.
The goal is to test if this would work with the pomodoro technique. I'd have a track which goes steady for 25 minutes, then an audio cue to take 5 and then another audio cue to start work again.