Ensuring every element of the track can be heard clearly and in balance, through any playback system is a difficult challenge, but one I rise to with every job. Translatability is key.
Understanding how every move I make will change the listener's emotional response to the track. And finding the best combination of processing units to achieve the most profound emotional response from the listener.
Observing and understanding various metering types to gain information. Mastering being the last stage of the creative process means quality control is imperative.