Main config file is named mixxx.cfg.
Midi config files end on .midi.cfg. The format goes like this:

Each group starts with a line like:
[Master]
or
[Channel1]
or
[Channel2]

For each group follows a number of lines, one for each control, eg.:

crossfader <midi no> <Key/Ctrl> [ch <channel no>]

Either a Key event or a Ctrl event is mapped. Take a look at, for instance,
the Midi-Keyboard.midi.cfg file, which maps many midi keyboard keys to buttons
in Mixxx, and uses the Modulation wheel for crossfading.

"ch" indicates a channel number, between 1 and 16, if omitted channel 1 is 
assumed.

Channel 19 is used for Joysticks.

Send mail to mixxx-devel@lists.sourceforge.net for further help.
