For documenting purposes: I had compiling errors with seq_scales.c and seq_chords.c on my Mac (osx 10.7.5) with Xcode 4.5.2: Missing brackets near initializer. It’s most probably a quirk on this particular setup. It’s got something to do with arrays and unions within typedefs, needing different curly brackets.
In seq_scales.c I changed the scale data arrays to (double opening and closing curly brackets instead of single):
{{ 0, 2, 2, 4, 4, 5, 7, 7, 9, 9, 11, 11,"Major " }},
and in seq_chords the chord arrays to (extra curly brackets around the numbers)
{ {0, 4, 7, -1}, "Maj.I " },
And then it compiled properly!