Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1766/sett.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-16310-sett.ps) >>/Users/jc/w/tmp/Tune-16310-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1766/sett.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-16310-24CountryDances_1810_Button_Whitaker_Elegant.abc 181 ABC music file with the extracted tune(s)
Tune-16310-24CountryDances_1810_Button_Whitaker_Elegant.txt 181 Plain-text file with the extracted tune(s)
Tune-16310-get.log 7759 Log file, useful mostly for debugging
Tune-16310-sett.abc 141 ABC music file with the extracted tune(s)
Tune-16310-sett.ps 6 PostScript
Tune-16310-sett.txt 141 Plain-text file with the extracted tune(s)
These files should be available for 24 hours.