Set your metronome for 136 BPM.
 
Have a four 1/4-note count in.
Play a 12-bar blues progression.
Have an 8-bar bridge section.
Repeat the 12-bar blues progression once more.
End with a four 1/4-note finale.
 
 

I do lots of radio spots that have very specific time requirements.  Some even have partial second fades to interleave with the next spot, etc.  I do much of the work in Sonar, but still use Sound Forge for sample accurate exit times.  I know that doesn't answer the question within the Sonar space, but if you're going to do a lot of time specific work in the future, you'll need to find a highly granular editor that will do a time precise trim.  Another way to do that would be to get some sample accurate files and use them as timeline guides in separate tracks in Sonar... just thinking out loud here...
 
-D

DonM
I do lots of radio spots that have very specific time requirements.  Some even have partial second fades to interleave with the next spot, etc.  I do much of the work in Sonar, but still use Sound Forge for sample accurate exit times.  I know that doesn't answer the question within the Sonar space, but if you're going to do a lot of time specific work in the future, you'll need to find a highly granular editor that will do a time precise trim.  Another way to do that would be to get some sample accurate files and use them as timeline guides in separate tracks in Sonar... just thinking out loud here...
 
-D

+1 
 
Haven't done much of this work within Sonar, but have done a bit of it with back and forth via Sound Forge for similar needs (commercials or film productions).

It is all down to imagination
You either got it or you ain't

It has a lot more to do with math and science than it does imagination to produce a piece of music that is exactly 34 seconds long in sonar and give it the right feel.

Time-slipstretch the clip.

On radio, I always thought commercials were 15, 20, or 30 seconds.

Make it somewhere in the neighborhood of the target time and then use a program like Sound Forge to adjust the final version to exactly the time you need.  This is done daily for commercials and advertising music spots.

DonM
I do lots of radio spots that have very specific time requirements.  Some even have partial second fades to interleave with the next spot, etc.  I do much of the work in Sonar, but still use Sound Forge for sample accurate exit times.  I know that doesn't answer the question within the Sonar space, but if you're going to do a lot of time specific work in the future, you'll need to find a highly granular editor that will do a time precise trim.  Another way to do that would be to get some sample accurate files and use them as timeline guides in separate tracks in Sonar... just thinking out loud here...
 
-D

In SONAR use Audio Snap.
No Brainer with Sound Forge, a bit of trimming for start time/stop time and enter 34 seconds into the 'elastique time stretch plugin, hit OK and yer done.

https://www.youtube.com/watch?v=SIIvJkSLSfw