The answer is - it depends 
 
There is no "rule" which says you must keep your busses at a particular level
 
I'm sure you'll get a lot of responses from people much more knowledgable than myself, but I always aim to keep all my busses at a fader level of 0dB when mixing. If you've got your gain staging working properly at track level, then the buss levels should not need to be moved very much from 0dB
 
It's also easy to produce different mixes such as vocals 1dB up, drums 0dB down, that sort of thing.
 
But be aware that applying any sort of processing on your busses can, and often will, lead to level increases which might overload your mains - this must be avoided at all costs.
 
Busses are also useul for applying another level of compression, should your tracks need it, but be careful with the makeup gain.
It's always better to apply compression in stages rather than slam it all in one place.
 
Are you running ALL of your busses to a Master Buss (not to be confused with your Main Outs )
 
Sorry, I was going to write more but got to dash off

I guess my question more simply put might be, "On an instrument buss, with the fader at 0dB and the signal peak hitting say -18dB, does one adjust the trim so that both the fader and track signal level are at 0dB?" My understanding is that if we're talking about a TRACK - the answer is YES - you do adjust the trim, and then the fader accordingly. Does the same principle apply to a buss?
 
Or, is the fact that the actual buss peak signal level is -18dB, with the buss fader at 0dB, indicative of another problem or issue? 
 
I appreciate you asking the other questions, 'cause I am a Newb in many ways. Someone could be giving me the answer but I'm too whatever to realize it :-) I don't mean to argue with you or challenging you when I say I don't think my question is related to gain buildup due to compression, etc. Lastly, all tracks are going to one or more busses, and all busses are routed to the Master Buss, which feeds the Main Out's. No tracks or busses are going direct to the main outs.
 
Thx again. 

No, you don't really need for tracks and busses to run at 0 dB.   Just run through the tracks.  Two schools of thought - start w/ the most important track and mix from there, or do your rhythm track and mix from there.  I start w/ the rhythm first.  Most of the time track is recording at -18 dB, or -12, or - 6.  I don't force the tracks to 0 by use of gain, but mix them so it sounds right.  Drums will go to a buss.  I don't force that to 0 on the meter for the buss.  The only thing you really need to pay attention to is the master.  Tracks and busses can hit the red w/o damaging the sound, tho that isn't good practice.  I don't want my master out hitting 0, tho.
 
Unlike analog (loved my 38), digital doesn't create noise, mechanical or otherwise.  We slammed tape because that reduced noise and could sound good.  And unlike analog, digital doesn't have any flattering artifacts - tape compression, transformer softening, etc.
 
Keep the levels sane when you record and mix.  Your master can easily be bumped up a few dBs when mastered.  But let the mix breathe.
 
@

For me, I pretty much only use bus gains to bring them down when levels are too hot into the various FX. On the master bus, I almost always have a limiter at the end of the chain so I can use that as I set the average volume level for the track to trim some of those spikes.
 
I don't always do anything.
 
The most important use of gain imho is to set the level into your FX. Some FX distort when run too hot. Others handle it without distortion. I usually don't twiddle gain on tracks after I've got FX set. changing input gain can change how the signal gets compressed.

I really do appreciate the input, guys. AT, we have mutual friends. I used to play with the Coppertones, and Codger, here in Dallas, and we've shared several bills with that crazy girl band you may know. I am very much looking forward to hooking up with local DFW users and sharing knowledge, if there is such an opportunity.
 
Several points hit home. I just had to clear the buss thing up in my head. Although it took quite awhile, when the "light finally went on" about recording too hot, Peak/RMS, layering compression, etc. and so on things have begun to become clearer. Not that I completely got it. In hindsight it is humorous -record too hot - try to "master" it with fanatical enthusiasm, and then lament why it sounds so bad :-)
 
I feel like I should re-record everything I've done incorrectly over the past ten years. 
 
<sigh>
 
Thanks again. There will be many more questions.

Levels only matter in two places:
level in from hardware
level out to hardware
 
Level in is determined by the hardware. Sonar does not have an adjustment for this.
Once the audio is in sonar only the output level to the hardware is critical.
 
Sonar cannot clip. Some of the plugs do. Some do not.  I use the meters as basic references. But I often have tracks and buses way in the red. And for some plugs.
 
All tracks go to a MASTER MIX bus. 
My MAIN OUT BUS is the first bus and way easy to get to to adjust actual volume.  The effects bin contains panipulator, span,....  only monitoring plugs.
 
The MASTER MIX bus outputs to the first BUS labeled MAIN OUT. Not to b confused with Sonar's outs. I NEVER look at Sonar's "main outs."
 
The MASTER MIX bus is the final output for the project. I bounce/export through this bus. This is the bus where the meters matter.
 

Hey Dono,
 
yea, I recognize those bands.  I've seen you play.  Good stuff, good times.
 
Yea, the analog to digital change isn't really a negative, just parts of it.  You just have to resist the rock n roll urge of turn it all up to 11 (and wonder why the song doesn't breathe).  I usually only change buss vol to bring it down toward the end of mixing, or vol automate it as a last resort of squeezing the overall vol.  A dB or two, if I have to.
 
We had a local Sonar users group going for a while, but it just kind of expired.  Grapevine was a long haul in rush hour.  Dallas/Ft. Worth is just too damn big, even if you meet in the middle.  Give me a pm if you ever want to get together.  One of the negatives of digital is how cheap it is, and we all tend to hang out in our music dens, doing our own thing.  Every time I sit down w/ somebody (whether SONAR or what ever) there seems to be a moment when I go "Oh, you do it that way in one step while I'm using 3 or 4?"
 
Take care, and if I ever make it out I'll keep eye (or even two!) out for you on the scene.

Thx AT, I will PM you next week. I'm taking my wife and my guitar and heading to Nowhere, Colorado for the 4th. Can't wait!
 
Happy 4th of July, everyone.

alantubbs at sbcglobal dot net for a more direct line
 
love to hear some of that wicked guitar
@