Hi,
For version 0.6.2 the left and right piano parts have to be channel 3
for the left hand and channel 4 for the right hand. PB has been
designed to work with these files on this page
http://www.pianobooster.pwp.blueyonder.co.uk/ which follow this
convention. But for now you will have to manually edit the midifile to
match this convention.
Please can you post a link to the midifile that you want to use and I
will try and getting working in the next release of PB.
Thanks
Louis