You could also eliminate abcm2ps and abc2midi by distributing the converted postscript and midi files (I'd guess they'd amount to about 20Mb for 5000 abc files).

Based on what I found doing my CD-ROM projects, multiply that figure by 20. A bit less if you use less space-hungry formats than PostScript.

It might save on CPU if graphic and midi files were converted on request, but stored at Mudcat rather than immediately disposed of, so that if a tune has been converted before it can just be fished out of store and resent.