Mastering is a process used to balance and optimize the sound of a stereo mix. It involves using state-of-the-art tools such as equalization, compression and limiting. It will also involve the diagnostic and repair of issues relating to polarity, phase and correlation while improving the stereo field for stereo playback while ensuring the audio can be reproduced on mono systems; such as those that might be used in enviroments such as nightclub lounges. Mastering an album includes transitioning and sequencing songs to ensure that playback of the music sounds consistent.