Test the microphone signal chain before recording. If recording multiple singers, check each mic before each take. Each backing singer will have a different vocal volume, what is right for one may not be right for the other. If the red warning light on the mixing desk illuminates, move the "gain" slider dial down.
Record each backing track vocal individually, as opposed to as a group. Have each backing singer deliver their take one after other.
Click "File" once the final backing vocal is recorded. Select "New Audio" and name the track "Vocal sub mix," then click "Bus" and select "Bus 1."
Click on "Send To" on the left of the channel strip and select "Bus 1." Repeat for each track.
Click on "Vocal sub mix" and click "File." Select "Export as Wav."
Click "File" and select "New Audio Track." Click "File" again and click "Import." Select the "Vocal sub mix" wav file. Using a single sub mix file instead of multiple audio files allows you to mix, apply compression and equalization to the entire backing vocal, for a more coherent mix.
Press "Play" and let the track roll. Click "Effects" and select "Compression." Adjust the "Ratio" dial to determine the intensity of the effect to your taste. Compression tempers volume peaks and adds a boost to any quiet parts in the backing vocal mix, to help the audio sit better in the overall mix.
Click "Tools" and select "Equalization." Adjust the individual gain dials for each frequency band to enhance timbre of the backing vocals. For example, reduce the bass frequencies so that the collection of voices doesn't sound too "muddy."