DJ Techtools just ran a great story that explains how to extract individual stems from stem files using FFmpeg and Audacity. Their well working approach is a mixture of installation, configuration and drag and drop.
If you are using OS X and are comfortable on the command line, you might appreciate a different approach, allowing you to batch destem your stem files to a format of your choice. To do so, simply install FFmpeg, so that it is in the
PATH. Then download the BASH script destem.sh and make sure it's executable (
chmod u+x destem.sh) and in the
PATH as well (if you don't know how to do that, please do not ask me, but Mr. Google.).
Once installed, the script is pretty self-explanatory. Open a terminal window, go to the folder that contains your stems and type:
MyMac$ destem.sh aif .
This will destem all files in the current directory and encode the results in AIFF. Other formats are possible. To get a list, simply type:
Yep. Just don't give it any arguments. Explicitly supported are: m4a | flac | wav | ogg | aif.
PS: The script may fail, if there are less/more than 4 stems plus the original in a file. It really isn't the sharpest tool from the shed.
Image by Joshua Rappeneker