I have finally found an easy solution to splitting polyphonic WAV files to stereo tracks without having to split to mono files and then recombine those to stereo.
1. Install
FFMPEG.
2. Copy/move the WAV to the directory containing ffmpeg.exe, or copy ffmpeg.exe to the directory containing the WAV file.
3. Open a command prompt and navigate to the directory containing your WAV and FFMPEG.
4. Enter the appropriate command based on how many channels your PolyWAV contains, replacing [inputfilename] with the name of your WAV:
*FOR 8 CHANNELS*
ffmpeg -i inputfilename.wav -filter_complex "[0]pan=stereo|c0=c0|c1=c1[a]; [0]pan=stereo|c0=c2|c1=c3[b]; [0]pan=stereo|c0=c4|c1=c5[c]; [0]pan=stereo|c0=c6|c1=c7[d]" -map "[a]" 1_2.wav -map "[b]" 3_4.wav -map "[c]" 5_6.wav -map "[d]" 7_8.wav
*FOR 6 CHANNELS*
ffmpeg -i inputfilename.wav -filter_complex "[0]pan=stereo|c0=c0|c1=c1[a]; [0]pan=stereo|c0=c2|c1=c3[b]; [0]pan=stereo|c0=c4|c1=c5[c]" -map "[a]" 1_2.wav -map "[b]" 3_4.wav -map "[c]" 5_6.wav
*FOR 4 CHANNELS*
ffmpeg -i inputfilename.wav -filter_complex "[0]pan=stereo|c0=c0|c1=c1[a]; [0]pan=stereo|c0=c2|c1=c3[b]" -map "[a]" 1_2.wav -map "[b]" 3_4.wav
You can run the 8-channel command on a file containing fewer channels without problems. Just be aware you'll be left with silent stereo files for the channels that were not recorded.
I adapted this from one of the solutions found
here. The other solutions listed there all returned errors, as did the syntax found in the
official documentation.