Got HTTP status 404 Not Found for "http://roaringjelly.org/~jc/music/book/DftY/Preston.abc/1796"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-34587-1796.ps) >>/Users/jc/w/tmp/Tune-34587-get.log 2>&1" returned status 256
http://roaringjelly.org/~jc/music/book/DftY/Preston.abc/1796

Error exit status 256; here are some files to check:
[get.cgi V=1/1 B=0 scale=0.55 512x512 PNG]
filesizedescription
Tune-34587-1796.abc 149 ABC music file with the extracted tune(s)
Tune-34587-1796.ps 6 PostScript
Tune-34587-1796.txt 149 Plain-text file with the extracted tune(s)
Tune-34587-get.log 3955 Log file, useful mostly for debugging
These files should be available for 24 hours.