Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/MM2/sett.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-72961-sett.ps) >>/Users/jc/w/tmp/Tune-72961-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/MM2/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-72961-Independent_Hornpipe_1.abc 580 ABC music file with the extracted tune(s)
Tune-72961-Independent_Hornpipe_1.gif 0 Graphics Interchange Format, the proprietary scan-line picture format
Tune-72961-Independent_Hornpipe_1.ps 37378 PostScript
Tune-72961-Independent_Hornpipe_1.txt 580 Plain-text file with the extracted tune(s)
Tune-72961-get.log 10040 Log file, useful mostly for debugging
Tune-72961-sett.abc 140 ABC music file with the extracted tune(s)
Tune-72961-sett.ps 6 PostScript
Tune-72961-sett.txt 140 Plain-text file with the extracted tune(s)
These files should be available for 24 hours.