Getting the spectral balance perfectly right is one of the key skills you have to master on the way to become a professional sound engineer. But it's much more difficult than you might think, and the true reason for this is that our brains automatically filter out interfering resonances. But how then are we going to find these frequencies? Because if they remain in the mix, they will interfere with other instruments and on an emotional level we won't like the mix because all the ingredients will be fighting against each other rather than beautifully connecting with each other. After having corrected interfering frequencies, it's then all about using the EQ in a constructive way as an artistic tool to make the mix interesting and exciting, and last but not least, we can even influence the depth of field with the EQ.