I'm trying to use a bassoon sample library recorded with close mics with some strings and other instruments.   The bassoon sounds front and center, which is not so good.     Any ideas on using sonar's plug-ins, or other compatible plug-ins, to move the sound back into the mix better?  
 
Very brief excerpt at https://soundcloud.com/wi.../0565-33-mixdraft01mp3

would try to cut some 'presence' freqs (5024 Hz) by a few tenths with Sonitus EQ.
maybe check if the signal has some side information, with Channel Tools (or free Voxengo MSED plugin, which sounds a little tighter) and then bring down the mid portion a bit.

The simplest methods are volume (fader) and a touch of reverb (solo and use enough so you hear it, then back it off a smidge). Perceptually, things that are quieter/have slight reverb are further away.

Thanks for the ideas.   I put one of Sonar's EQs, "BT Equalizer BQ2S-3" on the track, reduced the default "middle" and "mid Freq" by 2-3, and it already moved back into the mix better.    

When you get a chance, look up "frequency masking." Basically things of only a few dB louder will dominate all else at that frequency. Another technique is "mirror EQ" to mitigate this, which is what you are doing.

And use a low pass filter to roll off some of the highs.

I threw this in another post this morning but also has applicability to the OP here - this video came to mind before, but I was replying on my phone, so my replies get a bit short at times. My apologies.
 
"A really nice video worth watching is Dan Worrall's mixing demo for FabFilter Pro-Q. Although this is geared toward that specific product, the concepts are universal, and his comments during the video are great advice. It is a 10 minute video, and can be found here: https://youtu.be/kSNYBbPAvKE This is a good overview of "mirror EQ" concepts which are important to mixing."

I agree with most here.   Bassoon sits back in an orchestra compared to strings, resulting in a greater reflective sound ratio and some high frequency roll-off.  Most importantly though, bassoon is literally the quietest instrument in the orchestra.  It has almost no sound projection, requiring careful orchestration on the composer's part.  Take the volume way down for a realistic balance, and try panning slightly off center, the bassoonist is never center unless it is a solo concerto.  

+1 AT (LP filter)
+1 on reverb
+1 Sonitus (no pro-channel woes)
 
(Not sure I'd reduce volume as the Sonitus LP filter reduces several dBs.)
 

Thanks.   Mettelus, that video, Dan Worrall's mixing demo for FabFilter Pro-Q, is very good, thank you.