would be nice to have a popup asking this

PilotGav
I've been using Sonar since the Cakewalk days. 
 
In X3 I just opened a Midi file and found the TTS was automatically instantiated and the midi tracks assigned to it!
 
How long has this been going on lol. Can we assign a different synth to auto attach?
 
Sometimes the little things surprise you the most!

Hah! Yes, this is a great new feature in SONAR X3. This is tied to the Cakewalk TTS-1 only. I'm no Product Manager, but from what I understood this feature was implemented so that when you double-click on .mid file from anywhere on your computer, SONAR will open up and allow you to hear your MIDI sequence without assigning anything. I've had some calls where first time users "cannot get any sound out of their MIDI" due to the disconnect about routing MIDI tracks to a synth and then to an audio track. This feature alleviates some of that frustration when opening the software and using it for the first time ever. 
-DG

How about telling them to Read The Manual. LOL

I love to spend a great deal of my time practicing my guitar w midi files that have nothing to do with guitar music ...
one could say , that for years I've been using SONAR as my practice buddy / instant guitar lesson teacher ...
 
I happen to really dig this new feature of X3 auto inserting the TTS for a general midi file  ….
 
Kenny

I've done/do that. LOL It beats using a record any day!

Yes , a lot of the music I wish I could play on the guitar ….they don't even have books for ...
 
I think it's a great way to learn new things musically , also the TTS sounds fine for a quick and dirty practice session ..
 
Kenny

I swore I was going to blow this off but did it anyway...
 
To re-assign X1 to X3 for midi files, I modified the following registry entries... the quickest way to do this is to type "regedit" above the Windows Start Button, then Edit->Find and type in "SONARPDR.exe" (Producer version)
 
Hitting F3 will find the next instance, and keep looking to the right for entries that actually have keys. Only the first four with key entries need to be checked if you want to re-assign X3 as "default"
 
These are:
 
HKEY_CLASSES_ROOT->Applications->SONARPDR.exe->shell->open->command
HKEY_CLASSES_ROOT->Applications->CakewalkBundleFile->shell->open->command
HKEY_CLASSES_ROOT->Applications->CakewalkMIDIFile->shell->open->command
HKEY_CLASSES_ROOT->Applications->CakewalkTemplateFile->shell->open->command
 
The two I boldfaced needed to be changed on my machine, double clicking on the key in the right pane will allow you to edit the path to the program. I simply changed the X1 to X3 for those two and exited the registry.
 
The first boldfaced key assigns which version of "SONARPDR.exe" Windows "recognizes," which is why I could not get Windows to see X3... the pointer was to X1.
 
The second boldfaced key points specifically to the application Windows will launch midi files with.
 
Edit: to reiterate the point of the thread, launching a MIDI file will only insert TTS-1 if your have no MIDI outputs assigned for SONAR.

I've just created a new test project in another daw and recorded three MIDI tracks using SI-Drum, SI-Bass and SI-Electric Piano and exported the three MIDI clips as a single standard MIDI file. Then I closed the daw and double-clicked the exported MIDI file, which opened X3 and created 4 tracks, like this: 
 

 
Strangely, the SI instruments are automatically loaded (but the first track/clip failed to show "SI-Drum Kit"), and TTS-1 is also loaded, with a blank track. But what I really don't understand is, a default drum map is automatically assigned to the three SI tracks. When I exported an existing project in another daw as a standard MIDI file and ran the same test last night, it did the same thing. All tracks had the default drum map. Very strange. What am I missing?
 
Edit: Sorry, I thought SI instruments were automatically loaded, but it was only TTS-1. It's just the MIDI data and track/clip names that were carried over from the standard MIDI file. But I have no idea why the drum map has to be assigned automatically...

The SI Drums need to be on channel 10. 

John
The SI Drums need to be on channel 10. 

 
Hmm....strange. I've just deleted the SI drum track in the other daw and exported only 2 MIDI clips (SI-Bass and SI-Electric Piano) this time. But when I open the exported file in X3, the two tracks are still loaded with the default drum map. I need to investigate more...