Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/i_cant_get_started.abc/jazz"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-75733-jazz.ps) >>/Users/jc/w/tmp/Tune-75733-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/i_cant_get_started.abc/jazz

Error exit status 256; here are some files to check:
[P=get.cgi V=1/1 B=0 scale=0.55 512x512 PNG]
filesizedescription
Tune-75733-get.log 13414 Log file, useful mostly for debugging
Tune-75733-jazz.abc 359 ABC music file with the extracted tune(s)
Tune-75733-jazz.ps 6 PostScript
Tune-75733-jazz.txt 359 Plain-text file with the extracted tune(s)
These files should be available for 24 hours.