I have created an audio playlist file (m3u) from a list of around 40 mp3s. I need to be able to combine/join these files into one large audio file (mp3 or wav) that maintains the order that they are in in the playlist file. Is there software - command line or gui - that can do this?
If they are all in the same directory, you can just
catthem to the output file.
cat *.mp3 > output.mp3
If the file names do not reflect the order that they appear in the playlist follow this tutorial to rename them accordingly.
To read the contents of the playlist file and then cat each song in turn,
while read -r line; do cat "$line"; done < playlist.m3u > output.mp3
Note that this will give you one mp3 file containing all the songs, the metadata will probably not be correct. The output file will play fine though. (I've just tried it).