Got HTTP status 404 Not Found for "http://john-chambers.us/~jc/music/book/1769/LondonMagazine.abc"
pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-6854-LondonMagazine.ps) >>/Users/jc/w/tmp/Tune-6854-get.log 2>&1" returned status 256
http://john-chambers.us/~jc/music/book/1769/LondonMagazine.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-6854-LondonMagazine.abc 151 ABC music file with the extracted tune(s)
Tune-6854-LondonMagazine.ps 6 PostScript
Tune-6854-LondonMagazine.txt 151 Plain-text file with the extracted tune(s)
Tune-6854-get.log 4152 Log file, useful mostly for debugging
Tune-68540-get.log 3937 Log file, useful mostly for debugging
Tune-68542-24CountryDances_1826_Goulding_dAlmaine.abc 175 ABC music file with the extracted tune(s)
Tune-68542-24CountryDances_1826_Goulding_dAlmaine.pdf 2217 Portable Data Format
Tune-68542-24CountryDances_1826_Goulding_dAlmaine.ps 6 PostScript
Tune-68542-24CountryDances_1826_Goulding_dAlmaine.txt 175 Plain-text file with the extracted tune(s)
Tune-68542-get.log 5696 Log file, useful mostly for debugging
Tune-68549-003_Yankee_Doodle.abc 1385 ABC music file with the extracted tune(s)
Tune-68549-003_Yankee_Doodle.ps 37541 PostScript
Tune-68549-003_Yankee_Doodle.txt 1385 Plain-text file with the extracted tune(s)
Tune-68549-get.log 4658 Log file, useful mostly for debugging
These files should be available for 24 hours.