Hello again friends,
here's the issue: I wanna swap vocals in a (sonar) project to make a mashup,
there are no tempo changes, key matches perfectly without need of any adjustments (this is why the idea for mashup),
how can I sync the tempo of the imported (stereo) vocal track with the project?
AudioSnap appears to do nothing useful (average tempo detected incorrect, clip follow project results incorrect, vocal track gets stretched etc..), manually building all the transients and tempo map from scratch doesn't sound fun at all, afterall I don't need any individual between-notes tempo adjustments,
when I seek for help at google search, I'm presented with this sonar documentation which looks like a bad joke,
I ran across this sonar documentation which appears to be most suitable for the task, yet the feature set fails to provide the accuracy I seek for - it doesn't have any tempo calculator, having only "percentage" option gives very rough, practically useless results (no decimals available),
am I supposed to seek for different daw to accomplish such task?
thanks in advance

I would probably approach it this way:
 
- Import the vocal into a separate new project.
- Trim and slide it so that a clear downbeat syllable in the audio is at 1:01:000.
- Start playback, count out 4-8 bars, and stop the transport on the next downbeat 
- Dial in the Now time to be right on that transient, and Shift+M to Set Measure/Beat At Now, entering the measure and beat you counted to.
- Note the new initial tempo that SONAR sets for the project.
- If that calculated tempo is very close to a whole number like 103.98, the tempo is probably 104 even.
- Import the audio into the mashup project and align the starting point.
- Calculate Clip Tempo/Project Tempo (hopefully less than 1.0 for best results) and enter that as the Stretch percentage in Clip Properties.
- If that precision isn't sufficient, Slip-stretch the clip (Ctrl+drag) to get the last clear downbeat transient to fall on the appropriate beat (should be nearby).
- Bounce/Freeze the audio with the appropriate Offline Algorithm set in Properties, and check out the result.
 
If this doesn't give good alignment everywhere (e.g. because the tempo of the vocal wasn't really constant in the first place), you might need to go back to the pre-rendered stage, and use Audiosnap to stetch different segments by different amounts using a minimal number of enabled markers at strategic points.

"Note the new initial tempo that SONAR sets for the project."
project is recorded by metronome of 150 and so it matches the tempo throughout the whole song accurately already,
"Calculate Clip Tempo/Project Tempo" yes I can use my tap metronome on my phone with accuracy of +/-1 but the percentage doesn't give accurate-enough result
"Slip-stretch the clip (Ctrl+drag)" OH this is what I completely forgot about! but seems not to work no matter how I bounce the clip
"Bounce/Freeze the audio with the appropriate Offline Algorithm" last time I used offline algorithms, sonar had problems exporting audiosnap adjustments correctly at all, so since then I use "same as online" whenever possible

tzzsmk
"Note the new initial tempo that SONAR sets for the project."
project is recorded by metronome of 150 and so it matches the tempo throughout the whole song accurately already,
 

I meant when you use Set Measure/Beat At Now in the separate project with the vocal in it, SONAR will reset the initial tempo to make the timeline hit the beat you specify. This gives a fairly precise average tempo.
 
IIRC the stretch percentage supports more precision than is displayed in properties, but slip-stretching might be necessary to achieve it. I don't actually use that function much, and am not at my DAW now, so couldn't verify. Will have to check it out later. 

well, I did a workaround:
imported the vocal in soundforge, tapped tempo on my phone, put that tempo as reference and 150 bpm tempo as target in elastique timestretch, it calculated it's 0,933 and bam it was done, all within a minute...

I just did a quick test. Calculated tempo from Set Measure/Beat on first two measures was 103.97. Project was 110. 104/110 = 0.94545. Entered 94.545% Stretch in Properties and got a spot-on fit.
 
What you did in Sound Forge should have worked just as well in SONAR.