I'm sure there's a way, but don't know where to look in the help docs for info.
 
What I've done is take an existing MIDI song with full instrumentation, and saved a copy with only the drum and bass tracks.  In the future, if I want to re-add one or more of the other tracks from the original copy, what's the easiest way to do that? A link to the documentation would suffice if you don't want to type it all out. :)  Thanks!

Export audio (solo and select the track and check export only selected tracks) with the from project, then import the audio track into the TO project.
 
For a midi track, I simply open both projects and copy and paste between them.
 
There may be easier ways to do this but this works.
 
Jim
 
PS - this works for audio tracks and you have to watch the tempos in both tunes to do this. 

If you use per project audio folders: Import audio-> browse to (drive) Cakewalk projects->project folder -> audio -> track you're looking for.
 
Rocky

There's also the old favorite: copy and paste. I do that all the time.

Select a track from the source song (audio or midi), copy or choose copy special, if you want extra stuff like markers, then select the target track in the new song and generally use paste special to make sure you paste it at the first measure.

Another method is the following

· Select the entire track you wish to move and select copy special to place it's contents in to the clipboard.  Make sure  you select all the relevant items that are in your source track.
 
· With the track still selected, save the track as a track template - that way you get a copy of all the track parameters, effects, and bus sends, etc.
 
· Open your designation protect.
 
· Insert from track template and insert the track you saved before.
 
· Move your now marker to the beginning of your project and select paste special. Make sure you select all the relevant items automation, markers, tempo changes if present and required.

Hopefully your pasted track should have the same contents and characteristics of the source.

Have both projects open
1.Click on the track number at the start of the track you wish to copy to select the whole track,  then press control>c
2.In the project you are copying to,  make sure the playback marker is at the start of the song.
3.Right click below the last track number and choose 'insert midi track' 
4.Click on the new midi tracks track number,  then press control>v
5.Set the output and channel Setting of the new track to match what it was in the original project. 
 

I guess there are a lot of ways to say it:
I open up both projects.
I select the track or tracks I want to copy.
Then switch the view to the other project.
I paste them into the track or tracks into the other project. (Paste special so that you designate the track number of the first track number where you want the tracks to be pasted.)
BTW - be care if there are different tempos!

If it is MIDI you want to copy to the new project, EXPORT the MIDI then IMPORT into the new project. There are still some anomalies copying and pasting (locations, start times, etc.). Export is a lot cleaner to preserve timing and performance.

And if it's audio just open up both projects side by side and Drag And Drop from one to the other.

For audio tracks, track templates will save the audio in the global audio directory when you save a track as a template.  Instantiating the template will pull the audio in with it.  This way you have the audio and settings in the new project.
 
IIRC from the last time I checked, MIDI tracks did not save there clips in templates.  For MIDI you could use a two-step process.  1) Save the track(s) as a template, 2) drag copies of the MIDI to the media browser.  To bring them in, Instantiate a track from the template, drag the MIDI from the browser.