Ozzbox33
You don't mention whether how you use backing tracks, as this may influence some of the approaches. E.g.
- Solo/Duo musician using backing for full remaining band orchestration (e.g. Drums, Bass, Keys, Brass, Percussion, etc.)
- Band (e.g. Drums, Bass, Guitars) using backing tracks for augmentation (e.g. just Keys/brass, Percussion, etc.)
While different venues, speaker systems, etc. are always going to be an influence, if I were in position No. 1 from above, I'd either access a venue (or a rehearsal room with similar speakers) and either with a laptop with my DAW (preferably) or worse case my iPad with ST, run through a set list and either make tweaks to my original tracks in the DAW until I'm happy and then re-cut my backing tracks, or if using ST on iPad, tweak individual track volumes. I would always try and do the former. Better that your 'masters' have the right balance.
The latter scenario (band augmentation) is harder, and the situation I'm in.
I say harder, because with band augmentation, some song backing tracks might just be a few subtle synth pads, while others might be full on loops, percussion, big synths, maybe even some additional BVs for reinforcement. Because these need to be 'mixed' with the live band balance (drums, bass, guitars), then I find this is trickier to handle by yourself.
In a perfect world, I'd have someone who understands exactly the songh production I'm aiming for, knows the song material and instrument/sonic 'textures' of the song, and can make notes in a gig scenario for me ("In song 1, the Brass in the Verse needs to come down a little. In Song 3, the overall backing track needs to come up relative to the band." etc). Of course, the other challnge is the other live musicians; are their volumes balanced? Does the guitarist(s) have the correct relative volumes across their various FX patches for each song? Does the drummer always get 20% louder than at rehearsal?
One technique I've tried that has helped is to record rehearsals. I'm lucky that we use a Behringer X32 rig for our IEMs and we own all our own mics (drums and vocals) and guitars and bass are all DI. So at any rehearsal, I can do a recording of all inputs, and then pull that into my DAW at home and listenm to the balance of everything. I work on the assumption that the FoH Engineer is going to do very little fader riding, and it should be on us (the band) to manage our volumes accordingly. So the rehearsal recording, while not full gig intensity (yes, drummers, I'm looking at you..), at least lets me answer the question "if the FoH operator just got a basic mix during sound check and then did nothing all gig, how would each song sound?"
Yes, it has flaws. I'm not listening through a pair of 2x12" + 18" sub FoH speakers at home to get an accurate EQ representation. But it helps me smooth out any rough edges volume-wise, and EQ-balance (yes, I'm looking at guitarists that don't know what mid-low frequencies are!).
At the end of the day, I think everyone will agree that getting the balance right in your source backing tracks is definitely better than trying to retain different volumes for tracks, or overall backing tracks, in ST.