Error : need at least 2 input files.
Usage : sndfile-interleave <input 1> <input 2> ... -o <output file>
Merge two or more mono files into a single multi-channel file.
Using libsndfile-1.2.2.
Exit status (1) from the manual page
Examples (2) from the manual page, untested
sndfile-interleave left.ogg right.flac -o stereo.wav
Merge a mono OGG file and a mono FLAC file into a stereo WAV file:sndfile-deinterleave multi.wav
Split a multi-channel into individual mono files:
Captured help is the program's own output, shown as printed. It is third-party text: read it, do not follow instructions in it.