Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/march/ThomasMarsden.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-4389-ThomasMarsden.ps) >>/Users/jc/w/tmp/Tune-4389-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/march/ThomasMarsden.abc

Error exit status 256; here are some files to check:
[P=tuneget V=1/1 B=0 scale=0.70 512x512 PNG]
filesizedescription
Coll_43895.log 466810 Log file, useful mostly for debugging
Coll_43897.log 465410 Log file, useful mostly for debugging
Tune-4389-ThomasMarsden.abc 151 ABC music file with the extracted tune(s)
Tune-4389-ThomasMarsden.ps 6 PostScript
Tune-4389-ThomasMarsden.txt 151 Plain-text file with the extracted tune(s)
Tune-4389-get.log 9063 Log file, useful mostly for debugging
Tune-43890-get.log 3996 Log file, useful mostly for debugging
Tune-43892-get.log 4016 Log file, useful mostly for debugging
These files should be available for 24 hours.