pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-26581-20942_Mill_Mill_O.ps) >>/Users/jc/w/tmp/Tune-26581-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/ERM/20942_Mill_Mill_O.abc

Error exit status 256; here are some files to check:
[get.cgi V=1/1 B=0 scale=0.55 512x512 PNG]
filesizedescription
Coll_26581.log 454210 Log file, useful mostly for debugging
Form_26581.log 2025 Log file, useful mostly for debugging
Tune-26581-20942_Mill_Mill_O.abc 584 ABC music file with the extracted tune(s)
Tune-26581-20942_Mill_Mill_O.ps 35116 PostScript
Tune-26581-20942_Mill_Mill_O.txt 584 Plain-text file with the extracted tune(s)
Tune-26581-get.log 4511 Log file, useful mostly for debugging
These files should be available for 24 hours.