Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-6139-reel.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-5526-tmp.ps) >>/Users/jc/w/tmp/Tune-5526-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-6139-reel.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_5526.log 268010 Log file, useful mostly for debugging
Coll_55263.log 476611 Log file, useful mostly for debugging
Coll_55264.log 472410 Log file, useful mostly for debugging
Coll_55266.log 38669 Log file, useful mostly for debugging
Coll_55268.log 275010 Log file, useful mostly for debugging
Form_55265.log 895 Log file, useful mostly for debugging
Tune-5526-get.log 46283 Log file, useful mostly for debugging
Tune-5526-tmp.abc 156 ABC music file with the extracted tune(s)
Tune-5526-tmp.ps 6 PostScript
Tune-5526-tmp.txt 156 Plain-text file with the extracted tune(s)
Tune-55262-get.log 16579 Log file, useful mostly for debugging
Tune-55266-get.log 6020 Log file, useful mostly for debugging
Tune-55267-get.log 8742 Log file, useful mostly for debugging
Tune-55268-get.log 26338 Log file, useful mostly for debugging
Tune-55269-get.log 4066 Log file, useful mostly for debugging
These files should be available for 24 hours.