For me control room monitoring balance when tracking backing vocals is uber important.
The performers mix has to be separate.. (usually they want themselves louder than the rest of the music)
In the control room while setting up any adjustments to the new incoming BV signals I think you have to have one hand on the fader levels pretty much full time.. This is so you can hear the BLEND..
Once you have selected the best mic to proceed with..
Look for evenness - are some lines to quiet or too loud? (even when you have asked the performer to adjust that themselves) then use compression (or fader rides while recording) to get everything you want audible..
Tone? I like to have good eq control of upper mids available to me.. Also do you need to scoop out low mid 'boom' (again its best to do that by mic selection and position before touching EQ)
All the above adjustments should be made with a constantly adjusted monitor balance - you may want to make final tweaks by listening to the mix + vocal balance playing through a boom box.. In fact the lower volume monitoring can:
a) be a nice break for your ears as you move towards the mixing stage of the project
b) help you and the artist (on playback) spot pitch anomalies that you both might miss at full volume on headphones or the 'big' monitors. (relative pitch detection is way easier to do at low volume)
My favorite tweaker tool for stacked vocals used to be a TLA EQ1 mic pre / EQ. I would just use it in line in mode (using another mic pre) so only the eq section. I found the 'grainy' sharpness to the upper mids helped give BVOX 'air' and definition
.. I would "custom EQ" each new BV part to make it 'fit' into the stack.
Mic pre (various)
Line in Focusrite 215 channel A eq
Line in Focusrite 215 channel B eq
Sometimes Line in TLA EQ 1 DBX 902
Tape / DAW
You can hear this chain on the vocals on this whole album where I engineered and produced the vocal sessions.
Here is a busy track with a lot of stacked BVs (its a sort of Beachboys / indie rock hybrid) Carrie â€“ Can't Make Love â€“ Video & free listening at Last.fm