Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/Aird/Aird_vol4.abc/abc1"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-76611-abc1.ps) >>/Users/jc/w/tmp/Tune-76611-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/Aird/Aird_vol4.abc/abc1

Error exit status 256; here are some files to check:
[get.cgi V=1/1 B=0 scale=0.55 512x512 PNG]
filesizedescription
Tune-76611-OnceILovedAMaidenFair_PLFD1651_074.abc 353 ABC music file with the extracted tune(s)
Tune-76611-OnceILovedAMaidenFair_PLFD1651_074.ps 32139 PostScript
Tune-76611-OnceILovedAMaidenFair_PLFD1651_074.txt 353 Plain-text file with the extracted tune(s)
Tune-76611-abc1.abc 151 ABC music file with the extracted tune(s)
Tune-76611-abc1.ps 6 PostScript
Tune-76611-abc1.txt 151 Plain-text file with the extracted tune(s)
Tune-76611-get.log 9741 Log file, useful mostly for debugging
These files should be available for 24 hours.