Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/cache/Tune-4538-reel.abc/tmp"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-5396-tmp.ps) >>/Users/jc/w/tmp/Tune-5396-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/cache/Tune-4538-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_5396.log 322230 Log file, useful mostly for debugging
Coll_53962.log 472408 Log file, useful mostly for debugging
Coll_53963.log 75839 Log file, useful mostly for debugging
Coll_53967.log 265209 Log file, useful mostly for debugging
Coll_53968.log 459810 Log file, useful mostly for debugging
Form_53960.log 914 Log file, useful mostly for debugging
Form_53961.log 932 Log file, useful mostly for debugging
Form_53966.log 858 Log file, useful mostly for debugging
Tune-5396-get.log 9125 Log file, useful mostly for debugging
Tune-5396-tmp.abc 156 ABC music file with the extracted tune(s)
Tune-5396-tmp.ps 6 PostScript
Tune-5396-tmp.txt 156 Plain-text file with the extracted tune(s)
Tune-53960-get.log 175977 Log file, useful mostly for debugging
Tune-53962-get.log 4341 Log file, useful mostly for debugging
Tune-53963-get.log 9067 Log file, useful mostly for debugging
Tune-53964-get.log 4841 Log file, useful mostly for debugging
Tune-53965-get.log 7097 Log file, useful mostly for debugging
Tune-53966-get.log 5423 Log file, useful mostly for debugging
Tune-53967-get.log 9048 Log file, useful mostly for debugging
Tune-53968-get.log 6219 Log file, useful mostly for debugging
Tune-53969-get.log 8266 Log file, useful mostly for debugging
These files should be available for 24 hours.