I use an outside reliable  tuner ...I tune to 440 ...I play guitar for 45 years ...I know how to tune ....My problem is I record in perfect tune ...However when I play along and or  record another track and  I tune to 440 again ...Sometimes its not in tune with the recorded guitar track ? ... I record guitar direct in to the fireface ufx interface ... This problem is driving me crazy ...Its not ..me ..ugh .. THANK YOU ALL I CHECKED THE SAMPLING RATES ...THEY WERE THE SAME 44 ON THE INTERFACE AND SONAR ..
 
 OK HERE'S THE REMEDY ...IM USING A FIREFACE UFX ....it has the pitchslider ...it was off by 20% ...So that was my problem ...its zerod out now and all is fine ...Thank you everyone !

 
Are the sample rates of your interface and your Sonar project the same ?
 

Are the 2 recordings only slightly out of tune or nearly a half step? If they are nearly a half step then Paul P is probably on the right track. If Sonar thinks it is recording at say 44.1khz and the interface is set for 48khz (or vise-versa) then this kind of thing can happen. 

I think Paul P and Tom Riggs have got it figured out.
 
Does an A440 when played back sound like nearly an A#?  If so, then you are probably recording at a 44.1 KHz sample rate and playing back at a 48 KHz sample rate.  Does an A440 when played back sound a bit sharper than a G#?  If so, then you are probably recording at 48 KHz sample rate and playing back at a 44.1 KHz sample rate.  You might also detect a slight difference in tempo?
 
You just need to make sure SONAR and your audio interface agree on the sample rate in use.

Also, not all recordings are in tune either, meaning the track you are playing to may have been released that way.

I realize some tracks are released that way ....Just talking about my recordings ..

You need to define "how far" out of tune. other wise how can we help? 

This may not be relevant for your case, but sometimes a higher dynamic level will bring out things in a recording that had been obscured at a lower dynamic level -- I frequently work with volume very low, for my ears' sake, but sometimes have accidentally included bad sounds because they weren't apparent until raising the volume. 

Cactus Music
You need to define "how far" out of tune. other wise how can we help? 

Actually, even if he is tone deaf, a 44.1K to 48K sample rate mismatch will produce a 9% change in tempo and duration of the recording. So if he just has time sense or a stopwatch he can rule out that possibility.