Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1771/SCD_Book49-V1.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-6590-SCD_Book49-V1.ps) >>/Users/jc/w/tmp/Tune-6590-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1771/SCD_Book49-V1.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-6590-1803_Bland_Weller.abc 16672 ABC music file with the extracted tune(s)
Tune-6590-1803_Bland_Weller.pdf 187658 Portable Data Format
Tune-6590-1803_Bland_Weller.ps 128245 PostScript
Tune-6590-1803_Bland_Weller.txt 16672 Plain-text file with the extracted tune(s)
Tune-6590-SCD_Book49-V1.abc 150 ABC music file with the extracted tune(s)
Tune-6590-SCD_Book49-V1.ps 6 PostScript
Tune-6590-SCD_Book49-V1.txt 150 Plain-text file with the extracted tune(s)
Tune-6590-get.log 23114 Log file, useful mostly for debugging
Tune-65905-Nonesuch.ps 33472 PostScript
Tune-65905-get.log 4401 Log file, useful mostly for debugging
Tune-65906-get.log 4242 Log file, useful mostly for debugging
Tune-65908-get.log 6042 Log file, useful mostly for debugging
These files should be available for 24 hours.