Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-8117-Gow-CR-abc1.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-9601-tmp.ps) >>/Users/jc/w/tmp/Tune-9601-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-8117-Gow-CR-abc1.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_9601.log 315307 Log file, useful mostly for debugging
Coll_96011.log 478009 Log file, useful mostly for debugging
Coll_96012.log 454210 Log file, useful mostly for debugging
Coll_96013.log 273609 Log file, useful mostly for debugging
Coll_96014.log 741820 Log file, useful mostly for debugging
Coll_96015.log 478010 Log file, useful mostly for debugging
Form_96010.log 1399 Log file, useful mostly for debugging
Form_96011.log 185 Log file, useful mostly for debugging
Form_96018.log 903 Log file, useful mostly for debugging
Tune-9601-get.log 8588 Log file, useful mostly for debugging
Tune-9601-tmp.abc 163 ABC music file with the extracted tune(s)
Tune-9601-tmp.ps 6 PostScript
Tune-9601-tmp.txt 163 Plain-text file with the extracted tune(s)
Tune-96012-get.log 10306 Log file, useful mostly for debugging
Tune-96013-get.log 6460 Log file, useful mostly for debugging
Tune-96016-get.log 4953 Log file, useful mostly for debugging
Tune-96018-get.log 10064 Log file, useful mostly for debugging
Tune-96019-get.log 188728 Log file, useful mostly for debugging
These files should be available for 24 hours.