ZMidi

Copperbox revision 337.

I've improved the error reporting when parsing fails in ZMidi and the sample app MidiPrint.

MidiPrint will print a log of all the parsed Midi events up to the failure. Unfortunately ZMidi isn't so robust when parsing Midi files that are created by 'synthesizers' rather than programs like abc2midi or LilyPond. Files created by synthesizers can often have events that aren't accounted for in descriptions of the Midi file format that I've seen on the web.