Band-in-a-Box has an "Output Chords" feature that sends straight sustained chords to your MIDI Output Driver using a dedicated MIDI channel.
This feature is designed specifically for harmonizers like the TC Helicon VoiceLive 3, so that it can add harmonies to your vocals in real-time, following Band-in-a-Box's chord changes!
Read more about the VoiceLive 3:
http://www.pgmusic.com/tcheliconvoicelive3.htm TC Helicon recently released a free update for the VoiceLive 3, which includes many user-requested features!
Click here for more information about this free update.