Hi Joden,

All the MIDI that you play into Band-in-a-Box is played on the Thru track and each track can only be sent to one VSTi at a time. Splitting your MIDI input between two virtual instruments isn't supported natively by Band-in-a-Box but you may be able to work around it if you can find a VST that can host multiple instruments and route MIDI between them. Something like this http://www.bluecataudio.com/Products/Product_PatchWork/ might work for your needs.

You might also be able to achieve the same results if you have a VST that lets you split the keyboard range. Instead of having two totally separate plugins, you'd have one plugin load 2 different sounds, one for each region of the keyboard.

Regarding your second issue, it sounds like you're using an ASIO driver for your audio in Band-in-a-Box. When using an ASIO driver typically the program releases the driver when it isn't playing, which results in the entire program being silent. The only way you'd notice this is if you played an instrument while the song is stopped, which makes it look like a MIDI problem. You can fix this by going to Options | Preferences | Audio | Audio Drivers and checking the box "ASIO Always On." This makes sure the ASIO driver is always active so you'll always have sound, but it does tend to prevent any other programs on your computer from being able to access your sound card while Band-in-a-Box is open.