One of the challenges unique to the recording engineer is that he or she often doesn’t know the extent of the instrumentation for each song. Here’s a not-so-crazy scenario. A three-piece band goes to a studio and records some songs. The engineer achieves a tone that seems balanced when all three instruments are played back. Later, the band is struck by inspiration and decides that more instruments should be added. In adding more instruments, the previously attained tonal balance loses its equilibrium.
Understanding that the instrumentation may change, recording engineers are well-served by being willing to modify their approach to suit the known arrangement. Meaning that the focus will typically be on capturing each source in a way that is complementary to the original sound, the artist’s vision, and what instruments currently exist in the production. After all the recording is done, a fresh challenge awaits. It is the job of the mix engineer to take the numerous tracks in a song and make them fit together. That leads us to the mixer’s mindset.
The Mixing Engineer’s Perspective of Tonal Balance
The task of fitting a song’s tracks together requires a delicate “balance.” As a result, the concept of tonal balance for a mixing engineer is primarily about what results from the sum of all tracks. It’s not that it doesn’t matter what each instrument sounds like on its own; it’s just that what matters most is how everything sounds together.
With that in mind, mix engineers often have to make drastic tonal changes on a track-by-track basis to acquire the desired overall sound. For example, if the piano, bass guitar, and kick drum in a song each produce weighty low end in a similar frequency range, they fight for attention in that range while simultaneously yielding an overabundance of low frequencies in that territory. The engineer may do substantial equalization such as boosts and cuts in slightly different low frequency zones to allow each (piano, bass, and kick) to be individually distinguished while simultaneously creating an overall low end that is more spread out than before.
It’s challenging to carve and sculpt each track so that it sounds best not when it is soloed, but instead when it is mixed in with everything else. For the mixer, the big question is always, “Does it sound good when all the tracks are playing together?” As was the case for recording engineers, mixing engineers must factor in the arrangement and dynamics. The chorus really needs to hit hard? Well that’s not going to happen if the preceding verse sounds just full and loud as the chorus. Yeah, maybe the tonal balance needs to shift between song sections in order to achieve the right overall balance.
After a song has been mixed to a satisfactory degree, it may be tempting to use it as a reference when mixing other songs. Artists and engineers are constantly comparing current mixes to finished mixes. Doing so is both valuable and dangerous. It’s valuable to have something of greatness as a point of reference. Hearing a great mix can help steer you in the right direction and illuminate mistakes that you’re making. It’s common to reference other mixes during and after the development of the current one. Wouldn’t it be a lot easier to draw a platypus if you could reference a picture of one as you’re doing it? I rest my case. Back to music, though. Although referencing other mixes is often helpful, it can be counterproductive and even dangerous if the reference isn’t relevant to what is being mixed.
Let’s say that an artist requests his song sound like a popular tune. If the two songs have different instruments, there will be different amounts of frequencies in various areas. Even if the same instruments were used, different notes (in Song 1 vs Song 2) produce different frequencies and affect overall balance.
Imagine two songs with the same musicians and same instruments recorded back to back. In Song 1, the guitarist, keyboardist, and bassist play notes mostly in low registers, producing a lot of low-end energy. In Song 2, they play notes mostly in mid to high registers, producing less low-end energy and more mid- and high-end energy. Not only will the two songs have dissimilar tonal balances, it would be a mistake to make them identical. The same applies to songs in different genres. The image below shows the frequency curves of a folk song (white line) and a rap song (blue line). Notice that the rap song has more energy in the low end and high end, but less in the low mids.