Got HTTP status 404 Not Found for "http://roaringjelly.org/~jc/music/book/DftY/Skillern.abc/1799"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-21438-1799.ps) >>/Users/jc/w/tmp/Tune-21438-get.log 2>&1" returned status 256
http://roaringjelly.org/~jc/music/book/DftY/Skillern.abc/1799

Error exit status 256; here are some files to check:
[get.cgi V=1/1 B=0 scale=0.65 512x512 PNG]
filesizedescription
Tune-21438-1799.abc 150 ABC music file with the extracted tune(s)
Tune-21438-1799.ps 6 PostScript
Tune-21438-1799.txt 150 Plain-text file with the extracted tune(s)
Tune-21438-get.log 3963 Log file, useful mostly for debugging
These files should be available for 24 hours.