In this way, the cut-outs will remove frequency conflicts of the lead and back vocals in entire music. As the next step, if desired the engineer can use high-shelf EQ – by either enhancing audio top end for larger brightness of the whole song or, on the contrary, reducing it in order to put back vocals to the background and to give it more depth. As far as BVs online mixing and mastering sets in when the instrumental part of the music is ready, the filtration of a sub low audio element will be necessary in a far greater degree to avoid track dirtiness and a conflict with the other instruments. Most studios apply a low cut filter in the range of 100–200 Hz – it’s a norm in vocal professional mixing services. In the case with BVs, this norm can be higher, or additional equalization of around 200–500 Hz can be needed.
Everything depends here on the audio engineer’s taste and the precise song. If the music is loaded with thick wall of instruments, back vocals can be left on the whole dry (at most you can use delay) in order not to transform the track into muddle. If the overall music sound is dry and transparent enough, short reverberation (room) will suit. Flourish and abundant reverberation will not only let the engineer put BVs to the track depth but can also be an excellent creative solution.
This technique isn’t necessary during back vocals professional online audio mixing mastering, but it can sometimes be needed even if after previous steps there is a conflict with LV. In this case, the compressor is last to be put into the plugin chain of BVs group. It’s controlled by the main vox along the side chain. Some engineers use this technique only for a narrow frequency band (usually high mids).