In Part 3 of this series, we set levels for optimum signal-to-noise before clipping. So what do we start with first and how do we keep levels from creeping back up to overload as we add more instruments?
There are two basic schools of thought regarding where to start. Some mixers start with drums and bass and then add instruments, saving the vocals for last. The problem with this method is that as instruments are added, volume increases leaving less headroom by the time we get to vocals.
Some mix engineers using analog gear would set the kick drum and bass levels to average between -5dB and -7dB on the VU meters with the snare hits at up to 0dB. Of course, digital and analog meters respond differently, but this approach is still useful.
The other method is to start with vocals at an average level of 0dB then add drums, bass, and other instruments without ever boosting vocals. Since vocals are the focus of the song, using vocals as a ceiling helps ensure that instrument levels are brought in to support and not out-shout them. A good compromise between the two methods is to set a level for drums and vocals first (you can use settings above as a starting point) and then fill in the blanks with other instruments. The advantage of this approach is that once drums and vocals have a good balance and the right energy, the rest is gravy.