Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/Book23/Gow-CR-abc1.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-7257-Gow-CR-abc1.ps) >>/Users/jc/w/tmp/Tune-7257-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/Book23/Gow-CR-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
Coll_72570.log 291356 Log file, useful mostly for debugging
Coll_72571.log 287140 Log file, useful mostly for debugging
Coll_72572.log 282925 Log file, useful mostly for debugging
Coll_72576.log 288545 Log file, useful mostly for debugging
Find_72574.log 1558 Log file, useful mostly for debugging
Tune-7257-Gow-CR-abc1.abc 150 ABC music file with the extracted tune(s)
Tune-7257-Gow-CR-abc1.ps 6 PostScript
Tune-7257-Gow-CR-abc1.txt 150 Plain-text file with the extracted tune(s)
Tune-7257-get.log 9317 Log file, useful mostly for debugging
Tune-72570-get.log 5321 Log file, useful mostly for debugging
Tune-72571-get.log 1488 Log file, useful mostly for debugging
Tune-72578-EliasHowe_MusiciansCompanionP1-1842-V1.abc 177 ABC music file with the extracted tune(s)
Tune-72578-EliasHowe_MusiciansCompanionP1-1842-V1.txt 177 Plain-text file with the extracted tune(s)
Tune-72578-get.log 3700 Log file, useful mostly for debugging
Tune-72579-get.log 1539 Log file, useful mostly for debugging
These files should be available for 24 hours.