Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1766/dim.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-41800-dim.ps) >>/Users/jc/w/tmp/Tune-41800-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1766/dim.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-41800-CaledonianMusicalRepository_1811.abc 169 ABC music file with the extracted tune(s)
Tune-41800-CaledonianMusicalRepository_1811.ps 6 PostScript
Tune-41800-CaledonianMusicalRepository_1811.txt 169 Plain-text file with the extracted tune(s)
Tune-41800-dim.abc 140 ABC music file with the extracted tune(s)
Tune-41800-dim.ps 6 PostScript
Tune-41800-dim.txt 140 Plain-text file with the extracted tune(s)
Tune-41800-get.log 8528 Log file, useful mostly for debugging
These files should be available for 24 hours.