Hi and welcome to the Bome community!
This post should get you close, however you may need to adjust it so that you process notes above Middle C normally. For lowest note evaluation, it should probably bet set to middle C (note 60) and when something lower comes in, then you would not turn off any notes playing above middle C.
Steve Caldwell
Bome Customer Care
Also available for paid consulting services: bome@sniz.biz