My Sonar Platinum doesn't seem to do it. 
 
Everything's checked but nothing seems to go from the soft synth, which plays the initial midi track's information but does not bounce anything. I check everything that I know of to allow midi outputs from the synths, but that doesn't do it. Is there some kind of global off for midi bounce in the preferences?
 

Define "the soft synth" - which soft synth are you referring to? Not all soft synths support the MIDI out function - even it its selectable.

Synths that are capable of sending MIDI data have an option to "Enable Synth Output." Promidi is correct though, there are a few the have the option available but do not actually have the capability, DPro for one. But I suspect this is part of a series of posts about arpeggiator plug-ins. All of the arpeggiator VSTi's I have seen do send MIDI data when "Enable Synth Output" is checked,
 
There are a few places where the "Enable Synth Output" option may be viewed and edited.

• The insert synth options dialog
• The VST2/3 drop down in the standard header (see the "To enable VST MIDI input and output ports" section near the bottom of the page
• Or in the synth rack where the option is available from the synth settings menu and the context menu for each synth found by right-clicking the synth in the rack.

promidi, so far I've used Kontakt 5.5, TTS, and Dimension Pro, which all say that they have midi outputs.
 
scook, I have doubled-checked on the insert synth box, which indicates that there are midi outputs enabled, as well as right clicking the synths in the synth rack and double-checking the inputs and outputs on the channel strip. I have gone into the VST settings in the preferences menu and can't find anything that would turn midi echo on or off. In the VST Plug-In Properties in the VST Scan Paths>folder defaults, there was an unchecked box "Configure as tempo-based effect. That was the only box that seems to have anything to do with using a VST as an effect. I checked the box and nothing still seems to work.
 
Next?

TTS-1 is a DXi, it cannot send MIDI data
As I mentioned above DPro does not send MIDI data either yet shows the option in error.
I do not own Kontakt.
 
None of those would help solve your arpeggiator setup issue.
 
Setting "Configure as tempo-based effect" is the wrong thing to do for any synth. Arpeggiator VSTi are synths not tempo-based effects. Uncheck "Configure as tempo-based effect" and select "Configure as synth" as these options are mutually exclusive.
 
Rewriting the previous instructions using Kirnu Cream and TTS-1

• Add Cream using an instrument track, make sure  "Enable MIDI Output" is selected, set the track input to your controller and enable input echo.
• Add TTS-1 as an instrument track, set the input to the Cream 1 > MIDI Omni and enable input echo.

 
Hold down any note from 36 to 59 on your controller. Instead of playing one long note, it should play the arpeggiator output.

Midi track 1 goes to the TTS synth on track 2. Here's a problem, maybe, or maybe it's supposed to be this way. Track 2's output is to the main audio/sound out. While it's checked out to have midi output there is no box that you can use to send midi out that I can see. The midi output on the output box is faded out.
 
Obelisk track 3's input can be set to the TTS on track two, presumably getting the midi. Unfortunately, there is no midi going from track 2 to track 3. Is there some way to route track 2's midi to Obelisk that I can see, or is it done (or not done, in my case) automatically? 
 
Obelisk does not receive any midi and so no midi output goes to track four.
 
The problem seems to be between the midi output on track 2 (TTS) and the Obelisk. 
 
 
 

Scook, what soft synths actually have working midi outputs?
 
 

I closed the tempo-based box. The configure as synth box is faded out and cannot be checked. How would I open that up?
 

Bob In Portland
Scook, what soft synths actually have working midi outputs?

Every arpeggiator VSTi I have seen does. I cannot speak to Obelisk specifically but there is every indication from its main page that it does too

Obelisk is a MIDI plugin instrument that harmonises input MIDI and outputs it to your synths.

Bob In Portland
I closed the tempo-based box. The configure as synth box is faded out and cannot be checked. How would I open that up?

I have never tried changing a synth to a tempo-based effect and when I tried just now using Kirnu Cream VSTi  it does not disable the "Configure as synth" box in VST Properties. Please provide the plug-in name and exactly how you are trying to set the properties.