Double-click the desktop icon to launch your preferred digital audio workstation, for example Pro Tools or Logic.
Click "File" and select "Open." From the drop-down menu, select the session containing the harmonies for mixing.
Click the "Mixer" or "Mix Window" tab to view the mixing desk interface. This interface has slider dials to control the levels of each audio track.
Hit "Play" and click "S" on each audio channel. The "S" stands for solo. The solo function lets you hear each track in isolation. When you find a harmony track, typically like the lead vocal but at a different pitch, leave the "S" button turned on. Turn off the "S" button of all non-harmony tracks. Once complete, all you'll be able to hear are harmony tracks and the lead vocal.
Set the level of the lead vocal. Adjust the gain slider dial position so it is as close to the maximum as possible without triggering the red volume meter warning light. If the volume meter light illuminates, reduce the gain level. By setting it as high as possible, you set a maximum vocal threshold.
Adjust the gain of the first harmony track. Tracks are typically arranged left to right, so start on the left. Set it to approximately 70 percent of the level of the main vocal. Repeat this process so all channels containing the same harmony are at the same level.
Play the track all of the way through. Not all harmonies will appear at the same time, so it's prudent to listen through and double-check that nothing is spiking in the mix. If it is, identify the guilty track using the solo method and reduce the gain accordingly.
Click on the first harmony channel to highlight it and select "Send to." Click "Bus 1." In audio, a bus is a mix channel to route the output of multiple recording channels, enabling you to control a collection of audio with one fader.
Click on and route the remaining channels with the same audio to "Bus 1."
Group the remaining harmonies together on their own bus channels. This enables you to add effects, such as reverb and compression, to the harmonies as groups, rather than individual tracks. This ensures every harmony has the same effects as the others in its group.