Mixing and mastering are two processes which typically take place after recording.
Multi-track recording makes it possible to record various elements one by one on separate tracks. These elements may include voices, real instruments, programmed instruments, synthesised sounds and so on. Taking an example of a generic rock track, it would usually have elements like bass guitar, rhythm guitar, lead guitar, lead vocals, backing vocals and maybe a couple of synth tracks. Once all the tracks have been arranged and recorded, the mixing process is started.
During mixing, all the instruments in the song are carefully tweaked and adjusted to achieve the right sound. Achieving balance and clarity between different elements of the song is one of the main goals of mixing. It helps in making the final output easier to listen to and makes it sounds more professional.
The characteristics of the mix depend on the genre of music and the vision of what kind of song is being produced. Different genres and different styles of production demand different kinds of audio processing techniques. Commonly used audio effects are EQ, Compression, Reverb and Delay. Various other effects like auto-tune are also frequently used. A blend of all the elements in the right proportions without any element sticking out is one of the signs of a good mix. It also makes the next step, mastering, more effective.
Mastering is the process that is done after the final mix is ready. We are now looking at just one stereo track - The final mix.
Ensuring that your song plays back properly on various systems is a very important task. People listen to music on all kinds of playback devices ranging from cheap ear buds and laptop speakers to expensive headphones and speakers. Mastering ensures that the song sounds good on all kinds of playback systems. This is done using similar kinds of audio effects as discussed before, but using a more surgical approach. Obviously the song will not sound the same on all systems but it is a process of optimizing playback.
Loudness is another aim of mastering. There are certain guidelines for loudness level. These are measured in LUFS (Loudness Units Full Scale). Mastering ensures that the song has the desired level of loudness, stereo spread and frequency balance. It is one of the most important steps before a song is released commercially. When an EP/album is mastered, it helps connect each song together by keeping similar tonal balance, loudness, and the right balance of bass, mid and high frequencies.
Mixing and mastering is done keeping in mind the platform on which the song would be released (YouTube, Spotify, iTunes, movie theaters, etc). Mixing and mastering techniques also vary depending on the genre of music and the artist’s preferences. For example, classical and acoustic songs are usually more dynamic than electronic and pop songs.
In a nutshell, mixing and mastering are to music what Photoshop effects and Instagram filters are to pictures. During mixdown, the audio is processed with effects to enhance the sonic image. Mastering is the final polish that can help you achieve a clean, powerful, commercial sound.