Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/misc/MichaelDabney_12Minuets12Dances-1760-V1.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-680-MichaelDabney_12Minuets12Dances-1760-V1.ps) >>/Users/jc/w/tmp/Tune-680-get.log 2>&1" returned status 256
Error exit status 256; here are some files to check: