Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-5474-reel.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-2530-tmp.ps) >>/Users/jc/w/tmp/Tune-2530-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-5474-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_2530.log 475211 Log file, useful mostly for debugging
Coll_25303.log 283410 Log file, useful mostly for debugging
Coll_25309.log 455610 Log file, useful mostly for debugging
Form_2530.log 931 Log file, useful mostly for debugging
Form_25305.log 954 Log file, useful mostly for debugging
Form_25308.log 892 Log file, useful mostly for debugging
Tune-2530-get.log 3967 Log file, useful mostly for debugging
Tune-2530-tmp.abc 156 ABC music file with the extracted tune(s)
Tune-2530-tmp.ps 6 PostScript
Tune-2530-tmp.txt 156 Plain-text file with the extracted tune(s)
Tune-25300-get.log 25673 Log file, useful mostly for debugging
Tune-25305-get.log 15821 Log file, useful mostly for debugging
Tune-25306-get.log 12040 Log file, useful mostly for debugging
Tune-25307-get.log 20798 Log file, useful mostly for debugging
Tune-25308-get.log 6179 Log file, useful mostly for debugging
These files should be available for 24 hours.