Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-24641-march.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-4364-tmp.ps) >>/Users/jc/w/tmp/Tune-4364-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-24641-march.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_43642.log 1193231 Log file, useful mostly for debugging
Coll_43643.log 734821 Log file, useful mostly for debugging
Coll_43644.log 291811 Log file, useful mostly for debugging
Tune-4364-get.log 13870 Log file, useful mostly for debugging
Tune-4364-tmp.abc 158 ABC music file with the extracted tune(s)
Tune-4364-tmp.ps 6 PostScript
Tune-4364-tmp.txt 158 Plain-text file with the extracted tune(s)
Tune-43640-get.log 180331 Log file, useful mostly for debugging
Tune-43641-get.log 3216 Log file, useful mostly for debugging
Tune-43642-get.log 13314 Log file, useful mostly for debugging
Tune-43644-get.log 3082 Log file, useful mostly for debugging
Tune-43645-get.log 4040 Log file, useful mostly for debugging
Tune-43646-get.log 5712 Log file, useful mostly for debugging
Tune-43647-get.log 4555 Log file, useful mostly for debugging
Tune-43648-get.log 3885 Log file, useful mostly for debugging
Tune-43649-get.log 3439 Log file, useful mostly for debugging
These files should be available for 24 hours.