Today Source Filmmaker is releasing the Left 4 Dead Content Pack as its latest DLC! It contains the props, infected and all eight survivors from Left 4 Dead 2, including The Passing and The Sacrifice. They're also releasing music and voice, including all of the stems that were used to dynamically compose the distinctive music for Left 4 Dead. So now you can compose your own soundtrack out of those little snippets of oboe, banjo, saw and vocals to create something recognizably Left 4 Dead but also uniquely your own!
Both the SFM and L4D communities have been asking for this for a while, so we expect great things! Install Source Filmmaker, start the download from the Downloadable Content item in the File menu, and get animating!