Joining MP3 files can be rather simple task with a cat command. Suppose we have a directory with multiple MP3 files. The following cat command will join all MP3 files in a current directory to a single file called out.mp3:
Audacity is a great GUI for merging mp3 files, the whole of the file or you can copy and paste only what you want from a file.
Audacity is a great GUI for merging mp3 files, the whole of the file or you can copy and paste only what you want from a file. You can also increase and decrease volume, increase or decrease treble and bass, add tracks, normalize the two different files, change formats, add a track, fade in our out, and remove long lead in and lead outs. The most useful, versatile program for editing any mp3, wave, ogg file. Audacity will also convert Mp4 video to mp3 audio. You can also edit tags with Audacity.
Audacity will remove album art though, if you want album art you need Kid3 or Easytag to add the album art back.