pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-75723-1785_Cantelo.ps) >>/Users/jc/w/tmp/Tune-75723-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/DftY/1785_Cantelo.abc

Error exit status 256; here are some files to check:
[P=tuneget V=1/1 B=0 scale=0.70 512x512 PNG]
filesizedescription
Tune-75723-1785_Cantelo.abc 45204 ABC music file with the extracted tune(s)
Tune-75723-1785_Cantelo.ps 344513 PostScript
Tune-75723-1785_Cantelo.txt 45204 Plain-text file with the extracted tune(s)
Tune-75723-get.log 21009 Log file, useful mostly for debugging
These files should be available for 24 hours.