bouncing individual MIDI tracks when using one soft synth for several

I was able to get the piano by itself, maybe because it's in channel 1? But when I tried to bounce the bass, the piano came with it. I suppose I could live with a pre-mix like that, but I'd really like to keep 'em separate. The SI-bass guitar doesn't have an upright sound, and the one on the TTS-1 isn't awful, I'd like to use that. Creating a second instance of the TTS-1 didn't help, I still got both the piano and bass.

I always put each instrument's midi data for a multi-timbral synth (like Kontakt) into its own midi track, and in separate audio tracks as well.  Each loaded instrument gets its own midi channel, so that the single instance of the synth knows which instrument to route the associated midi data to.
 
That always works for me to bounce each instrument separately.
 
Please detail your audio/midi tracks and routing assignments for your instance of TTS-1.
 
Thanks, 
 
Bob Bone
 

Try adding an additional audio track for the bass part.
 
Create a new audio track
Change the new audio track input to the Cakewalk TTS-1 instance "Output 2: Stereo".
Open the TTS-1 UI.
Click the SYSTEM button on the TTS-1 UI.
Click the OPTION button on the SYSTEM SETTING dialog.
Make sure the "Use Multiple Outputs" is checked on the "Output Assign" tab and assign the bass part to OUTPUT 2.
 
Now the piano should play on the original audio track, the bass part on the new audio track.
 
 

All the track related to a synth will bounce or freeze sequentially with the same command.

If you are going to switch between different TTS-1 drum kits often, creating drum maps to perform the note translation would save some time. Otherwise, move the notes in the PRV. Notes may be selected by pressing the key (or note name) on the PRV keyboard. For drum kits, it may help to use note names instead of the piano keyboard. I believe the kits in TTS-1 line up with the note names supplied by the Roland GS drum kits listed in the Note Names dialog drop down. The Note Names dialog is displayed when right-clicking in the Track Pane keyboard in the PRV.