Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/ONeills/Rare_Small/0104_Big_Bow-wow.abc/book0"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-27078-book0.ps) >>/Users/jc/w/tmp/Tune-27078-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/ONeills/Rare_Small/0104_Big_Bow-wow.abc/book0

Error exit status 256; here are some files to check:
[get.cgi V=1/1 B=0 scale=0.65 512x512 PNG]
filesizedescription
Tune-27078-book0.abc 173 ABC music file with the extracted tune(s)
Tune-27078-book0.ps 6 PostScript
Tune-27078-book0.txt 173 Plain-text file with the extracted tune(s)
Tune-27078-get.log 4116 Log file, useful mostly for debugging
These files should be available for 24 hours.