Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1762/IaST-abc1.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-9403-IaST-abc1.ps) >>/Users/jc/w/tmp/Tune-9403-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1762/IaST-abc1.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-9403-IaST-abc1.abc 146 ABC music file with the extracted tune(s)
Tune-9403-IaST-abc1.ps 6 PostScript
Tune-9403-IaST-abc1.txt 146 Plain-text file with the extracted tune(s)
Tune-9403-get.log 4045 Log file, useful mostly for debugging
Tune-94031-get.log 1424 Log file, useful mostly for debugging
Tune-94038-10354_Copenhagen_Waltz.abc 715 ABC music file with the extracted tune(s)
Tune-94038-10354_Copenhagen_Waltz.gif 0 Graphics Interchange Format, the proprietary scan-line picture format
Tune-94038-10354_Copenhagen_Waltz.ps 35297 PostScript
Tune-94038-10354_Copenhagen_Waltz.txt 715 Plain-text file with the extracted tune(s)
Tune-94038-get.log 5826 Log file, useful mostly for debugging
These files should be available for 24 hours.