Launch your preferred digital audio workstation, also called a “DAW.”
Open the “File” menu and select the relevant mix from the “Recent” sub-menu. If your DAW is configured to automatically launch the last-saved session, you may not need to do this.
Click on the first vocal channel to highlight it. Click “Send” and select “Bus 1.” In audio, a bus is a group mixer channel. By sending a collection of audio to a bus channel, you can add effects and adjust the level of multiple audio tracks using a single set of control parameters.
Click on the remaining vocal channels individually and send them all to the “Bus 1.” This is how you create a sub-mix for mastering.
Click on “Bus 1” to highlight it. This assigns subsequent mastering edits to that channel, rather than the entire mix.
Open a multi-band compressor. The method for doing this varies slightly according to the DAW that you use, but you typically access effects from the “Effects” menu. A multi-band compressor enables you to boost the amplitude of specific frequencies within a sound. The multi-band compressor will open in a separate window.
Hit “Play” and monitor the display on the multi-band compressor. The sound of the grouped vocals is displayed visually, with volume unit meters for each frequency band. Each frequency band has its own slider dial to control the amplitude. There are typically four frequency bands.
Adjust the amplitude of each frequency by moving the slider dial. For example, if the vocal mix sounds a little thin, boost the bottom end by increasing the position of the dial farthest left. If it sounds “tinny,” cut some of the high-end frequencies by lowering the dial farthest right. While mastering is a matter of taste and aesthetics, you should aim for a balanced blend of all frequencies.
Quit the multi-band compressor.
Open a limiter from the effects menu. A limiter is similar to a compressor, but instead of boosting and cutting frequencies, you use it to limit the volume span between the loudest and quietest parts of the audio. This removes spikes and dips in the volume.
Tweak the “Threshold,” “Attack” and “Ratio” dials to set the limiter to your preference. For example, if you want a punchy, tight-sounding vocal, set the “Threshold” to around 70 percent, the “Attack” to around 50 percent and the ratio to approximately “2:1.” This configuration means the loudest 30 percent of the vocals are reduced in volume by half. The speed of that reduction is moderate, creating a smooth sound.