Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1792/cont.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-5390-cont.ps) >>/Users/jc/w/tmp/Tune-5390-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1792/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-5390-cont.abc 141 ABC music file with the extracted tune(s)
Tune-5390-cont.ps 6 PostScript
Tune-5390-cont.txt 141 Plain-text file with the extracted tune(s)
Tune-5390-get.log 3940 Log file, useful mostly for debugging
Tune-53903-get.log 1392 Log file, useful mostly for debugging
Tune-53907-get.log 1361 Log file, useful mostly for debugging
Tune-53908-Thompson_V2_1758-1765_FTM.abc 162 ABC music file with the extracted tune(s)
Tune-53908-Thompson_V2_1758-1765_FTM.ps 6 PostScript
Tune-53908-Thompson_V2_1758-1765_FTM.txt 162 Plain-text file with the extracted tune(s)
Tune-53908-get.log 4429 Log file, useful mostly for debugging
Tune-53909-FARNE_Anonymous1.abc 153 ABC music file with the extracted tune(s)
Tune-53909-FARNE_Anonymous1.ps 6 PostScript
Tune-53909-FARNE_Anonymous1.txt 153 Plain-text file with the extracted tune(s)
Tune-53909-get.log 4240 Log file, useful mostly for debugging
These files should be available for 24 hours.