Not all mixing tools are made equal. Some tools have a greater effect on the mix than others. Sometimes it helps to consider four types of tools – volume, tone, dynamics and ambience.
Volume is the most powerful mixing tool – the humble channel fader. If you only had one tool to do a mix, it’d have to be volume. Even in a more complex mix, it’s the most critical tool. No amount of EQ or compression or reverb can help you if the basic relative volumes of each track are wrong. Volume control of each track is essential to achieving an effective balance between foreground sounds (the focus on the mix) and the background sounds (the filling and depth of the mix).
Tone is the next most powerful tool. The tone of each channel is usually adjusted using EQ or filters. Tone control can be used in two ways – correcting problems in the sound of a track (such as unwanted resonance or treble/bass tilt) and supporting the depth in the mix (helping sounds appear closer the the foreground or further in the background).
Dynamics are almost as powerful as tone – but not quite. The dynamics of a channel can be adjusted using compression (for controlling loud parts of a recording) and gating/expansion (for controlling quiet parts of a recording). While powerful, dynamics are less useful than tone. While compression in particular can be useful for shaping the transients and the ‘feel’ of a sound, it’s less effective than volume and tone for adjusting the relative balance between the tracks in a mix.
Ambience is the least powerful of the four – it is the ephemeral cloud and subtle reflections that we use as cues to tell us the shape and size of the ‘space’. Ambience is often added with reverb and delay, but can also be manipulated by using dynamics processing to emphasise or de-emphasise the natural ambience in the raw recordings. Even though ambience is at the end of this list, it is still a very powerful tool. Like compression, it can often have an influence on the ‘feel’ of a mix – affecting the emotions rather than the function of a mix.