Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1800/cont.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-3403-cont.ps) >>/Users/jc/w/tmp/Tune-3403-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1800/cont.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-3403-cont.abc 141 ABC music file with the extracted tune(s)
Tune-3403-cont.ps 6 PostScript
Tune-3403-cont.txt 141 Plain-text file with the extracted tune(s)
Tune-3403-get.log 3940 Log file, useful mostly for debugging
Tune-34030-get.log 6128 Log file, useful mostly for debugging
Tune-34036-IaST-abc1.abc 146 ABC music file with the extracted tune(s)
Tune-34036-IaST-abc1.ps 6 PostScript
Tune-34036-IaST-abc1.txt 146 Plain-text file with the extracted tune(s)
Tune-34036-get.log 3972 Log file, useful mostly for debugging
Tune-34039-get.log 2959 Log file, useful mostly for debugging
These files should be available for 24 hours.