Mastering is the process of preparing and transferring recorded audio from a source that holds the final mix into a data storage device. This data storage device is known as a master. Mastering is the last step in the process of making a professional-sounding song. Mastering acts like a filter; a type of audio post-production that involves taking an audio mix and preparing it for proper distribution. 

The main purpose of mastering is to balance all the sound elements of a stereo mix, make all the elements sound consistent, and optimize playback so that it reaches the accurate loudness. Mastering adds depth, clarity, punch and volume to tracks. Mastering involves critical listening as well as the right skills. Mastering involves accurate speaker monitors, a pleasant listening environment, as well as consistency through a specific material. There are different types of masters, including analog masters and digital masters.

Mastering involves the application on several techniques, such as compression, limiting, and equalization. There are other operations that can become part of the mastering process, including noise reduction, editing, level adjustment, saturation, enhancement, as well as restoration. The audio mastering process is far from being one size fits all. The audio mastering process is quite variable and depends on the specific needs of a particular audio piece.   

Mastering is important but not essential. Sound engineers should pay attention to specific details in a mix in order to determine if the mastering process is necessary. When a mix has an adequate volume level, the equalization is consistent, the faders are balanced, and the compression is at its optimal level, the mastering process is not important. 

With mastering, songs sound great in all speakers. With mastering, songs achieve optimal volume levels. With mastering, achieve perfection. Mastering is a learning process that requires practice, patience, and consistency.