I have TTS Virtual Piano and SB External Media
You must mean SB External
MIDI
If the MIDI input is set to that, that is the SB's MIDI interface In. Ditto on the output. So a track with that as an input will recieve MIDI messages coming in the interface, and send its messages out to the output on the interface.
The source should be either MIDI OMNI -- which means that any MIDI messages coming in will be recorded regardless of what channel they are assigned to -- or any of the channels 1-16 that you want -- which means that only MIDI messages assigned to the channel you select will be recorded. Of course to select the appropriate channel, you have to know which MIDI channel the Roland is set up to send on.
The port will then be the appropriate channel on the Roland. Which you choose doesn't matter so much so long as every channel is assigned to a unique one of the available 16 channels. Say Track 1's Port is set to MIDI Channel 1. When you select a Bank and a Patch (say Acoustic Piano), the synth will respond to MIDI Note On messages coming from this track by playing them with the Acoustic Piano patch.
Bank Select method depends on what the Roland wants. If you are using the correct instrument definiton file for your synth, the Bank list will show you whatever banks the synth has availble (if any), and the Patch selection then displays the 128 patches available in the currently selected Bank. Banks are simply collections of Patches.
All this is fairly well spelled out in the Cakewalk manual/help system, and they have FAQs on their website too. It all makes perfect sense if you think it through and understand the definitions.
