Set BB to Voicemeeter Virtual ASIO.
Set other audio app to Voicemeeter AUX Virtual ASIO.
Set the Output to your main audio device.

You can also install VB Cable and set that as the default Audio Device for windows then set it as a Hardware Input in Voicemeeter, this way the green Demo button will play in the picker windows.

Not sure how you are using Cantabile exactly but another option is use I-L MiniHost vst/vsti http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=368498 within BB.

You can add another midiIn vst in it http://www.thepiz.org/plugins/?p=midiIn

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