Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-33374-SocialDances2002.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-1634-tmp.ps) >>/Users/jc/w/tmp/Tune-1634-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-33374-SocialDances2002.abc/tmp

Error exit status 256; here are some files to check:
[get.cgi V=1/1 B=0 scale=0.55 512x512 PNG]
filesizedescription
Coll_16343.log 1297409 Log file, useful mostly for debugging
Coll_16344.log 566818 Log file, useful mostly for debugging
Tune-1634-get.log 14678 Log file, useful mostly for debugging
Tune-1634-tmp.abc 169 ABC music file with the extracted tune(s)
Tune-1634-tmp.ps 6 PostScript
Tune-1634-tmp.txt 169 Plain-text file with the extracted tune(s)
Tune-16340-get.log 2803 Log file, useful mostly for debugging
Tune-16340-kalamatiano.abc 0 ABC music file with the extracted tune(s)
Tune-16341-get.log 181701 Log file, useful mostly for debugging
Tune-16341-kalamatiano.abc 0 ABC music file with the extracted tune(s)
Tune-16342-get.log 169915 Log file, useful mostly for debugging
Tune-16343-get.log 50026 Log file, useful mostly for debugging
Tune-16346-get.log 10511 Log file, useful mostly for debugging
Tune-16347-devetorka.abc 0 ABC music file with the extracted tune(s)
Tune-16347-get.log 2823 Log file, useful mostly for debugging
Tune-16348-get.log 7811 Log file, useful mostly for debugging
These files should be available for 24 hours.