Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-12888-dim.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-6394-tmp.ps) >>/Users/jc/w/tmp/Tune-6394-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-12888-dim.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_63942.log 732019 Log file, useful mostly for debugging
Coll_63948.log 758619 Log file, useful mostly for debugging
Find_63947.log 1447 Log file, useful mostly for debugging
Form_63940.log 1172 Log file, useful mostly for debugging
Form_63941.log 984 Log file, useful mostly for debugging
Form_63943.log 1011 Log file, useful mostly for debugging
Form_63946.log 870 Log file, useful mostly for debugging
Tune-6394-get.log 3969 Log file, useful mostly for debugging
Tune-6394-tmp.abc 156 ABC music file with the extracted tune(s)
Tune-6394-tmp.ps 6 PostScript
Tune-6394-tmp.txt 156 Plain-text file with the extracted tune(s)
Tune-63942-get.log 5105 Log file, useful mostly for debugging
Tune-63943-get.log 5933 Log file, useful mostly for debugging
Tune-63948-get.log 36830 Log file, useful mostly for debugging
These files should be available for 24 hours.