Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-22791-was.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-1659-tmp.ps) >>/Users/jc/w/tmp/Tune-1659-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-22791-was.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_16590.log 575221 Log file, useful mostly for debugging
Coll_16596.log 737619 Log file, useful mostly for debugging
Form_16596.log 956 Log file, useful mostly for debugging
Form_16597.log 849 Log file, useful mostly for debugging
Sess-16598.log 441 Log file, useful mostly for debugging
Tune-1659-get.log 3967 Log file, useful mostly for debugging
Tune-1659-tmp.abc 156 ABC music file with the extracted tune(s)
Tune-1659-tmp.ps 6 PostScript
Tune-1659-tmp.txt 156 Plain-text file with the extracted tune(s)
Tune-16590-get.log 171748 Log file, useful mostly for debugging
Tune-16592-get.log 5553 Log file, useful mostly for debugging
Tune-16593-get.log 9259 Log file, useful mostly for debugging
Tune-16595-get.log 4381 Log file, useful mostly for debugging
Tune-16597-get.log 1709 Log file, useful mostly for debugging
Tune-16598-get.log 5399 Log file, useful mostly for debugging
These files should be available for 24 hours.