c:
cd %~dp0
mkdir Spectrograms
FOR %%A IN (%*) DO sox %%A -n remix 1 spectrogram -x 3000 -y 513 -z 120 -w Kaiser -o "Spectrograms\%%~nxA-full.png"
FOR %%A IN (%*) DO sox %%A -n remix 1 spectrogram -X 500 -y 1025 -z 120 -w Kaiser -S 1:00 -d 0:02 -o "Spectrograms\%%~nxA-zoom.png"
pause
Not sure if that's intentional but "remix 1" will pick only the left channel. You need either "remix 1-2" or "channels 1" if you want them mixed (or nothing if you want separate spectrograms per channel):
sox -r44.1k -c2 -n -b24 L1k-R5k.wav synth 5 sin 1k sin 5k fade 0.2 0 0.2 norm -6
sox L1k-R5k.wav -n remix 1 spectrogram -x 1136 -o remix1.png
sox L1k-R5k.wav -n remix 1-2 spectrogram -x 1136 -o remix12.png
sox L1k-R5k.wav -n channels 1 spectrogram -x 1136 -o channels1.png