A few questions back, to try get some focus (or to at least avoid dragging you into a direction you never wanted to go, heh):

What would be your desired outcome in terms of what you hear and where from you hear it?
Have you thought of fiddling with the "Local On/Off" setup in BBox preferences?
Precisely how are you connecting your Yamaha to your Mac?

p.s. If "one chorus would be enough", perhaps simply setting your song to just one chorus before you start recording might be worth considering. You can always edit or add afterwards, if needed.

Just because you can, doesn't mean you should!
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BBox 2022 Audiophile, Mac Pro Intel, OSX 10.6.8, 800x600 (TV VGA)