SYNOPSIS
sndfile-mix-to-mono <multi-channel input file> <mono output file>
DESCRIPTION
sndfile-mix-to-mono reads a multi-channel input file and writes a single channel output file consisting of all of the input channels mixed together (like a audio mixing desk would do). The input and output files are read/written using libsndfile (http://www.mega-nerd.com/libsndfile/).The format of the output file is determined by the filename extension of the output file.