Makes "learning duets" out of learning tracks.
You should set up a temporary directory with symlinks for each part (lead, bari, bass, tenor), and then all 6 duets will be created when run in that temporary directory. By default, we try for tracks 1 through 12; use something like:
perl sox-make-learning-duets.pl --start=15 --end=15
to override that. Doesn't do well with single files; it assumes you have a whole album of tracks. (In particular, this was thrown together for working with Harmony Brigades.)
Requires sox (compiled with liblame), Perl, and the Time::HiRes and MP3::Tag Perl modules from CPAN.
Patches, suggestions, and some sort of test suite would be very welcome.
If the tracks you get aren't aligned (presumably because there are short intros of varying lengths added to the beginning), the duets won't be in sync. I recommend using Audacity to time shift them.
KNOWN BUGS
See issues.