Following this question I decided to use ffmpeg to crop MP3s. On another question I found this way of doing it:
ffmpeg -t 30 -acodec copy -i inputfile.mp3 outputfile.mp3
The problem is that I don't want to crop the first 30 seconds, I want to crop from x to x+n, like from 30s to 100s. How would I go and do this?
I'm reading the man for ffmpeg but this is not really straightforward, especially since I just discovered about ffmpeg and I'm not familiar with audio/video editing softwares, so any pointers would be appreciated.
Take a look at the -t and -ss arguments. They should do what you want.
For example,
ffmpeg -ss 30 -t 70 -i inputfile.mp3 -acodec copy outputfile.mp3
should do the trick for the range you mentioned (30s-100s).