Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1784/LondonMagazine.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-9739-LondonMagazine.ps) >>/Users/jc/w/tmp/Tune-9739-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1784/LondonMagazine.abc

Error exit status 256; here are some files to check:
[P=tuneget V=1/1 B=0 scale=0.70 512x512 PNG]
filesizedescription
Tune-9739-LondonMagazine.abc 151 ABC music file with the extracted tune(s)
Tune-9739-LondonMagazine.ps 6 PostScript
Tune-9739-LondonMagazine.txt 151 Plain-text file with the extracted tune(s)
Tune-9739-get.log 4146 Log file, useful mostly for debugging
Tune-97393-get.log 12548 Log file, useful mostly for debugging
Tune-97394-get.log 4019 Log file, useful mostly for debugging
Tune-97395-get.log 3409 Log file, useful mostly for debugging
Tune-97397-get.log 4400 Log file, useful mostly for debugging
Tune-97398-get.log 8657 Log file, useful mostly for debugging
Tune-97399-get.log 4341 Log file, useful mostly for debugging
These files should be available for 24 hours.