Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/JamesOswald/CPC/16221_Wallaces_March.abc/all"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-1374-all.ps) >>/Users/jc/w/tmp/Tune-1374-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/JamesOswald/CPC/16221_Wallaces_March.abc/all

Error exit status 256; here are some files to check:
[get.cgi V=1/1 B=0 scale=0.55 512x512 PNG]
filesizedescription
Coll_13740.log 457010 Log file, useful mostly for debugging
Coll_13747.log 462610 Log file, useful mostly for debugging
Form_13748.log 916 Log file, useful mostly for debugging
Tune-1374-all.abc 172 ABC music file with the extracted tune(s)
Tune-1374-all.ps 6 PostScript
Tune-1374-all.txt 172 Plain-text file with the extracted tune(s)
Tune-1374-get.log 4067 Log file, useful mostly for debugging
Tune-13741-get.log 4113 Log file, useful mostly for debugging
These files should be available for 24 hours.