Mixing is the technique of blending all of the individual tracks in a recording to create a version of the song that sounds as good as possible. This is called "the mix”.
The process can be comprised of:
- Balancing the levels of the tracks that have been recorded
- Fine-tuning the sound of each instrument or voice using equalization (EQ)
- “Panning” the tracks between speakers to create a stereo image
- Adding reverb, compression, and other effects to enhance the original recording
Mixing sometimes includes a bit of editing – choosing the best bits of every take of a song, and sometimes even building musical elements from scratch. Sometimes there is so much editing involved it forms a separate stage in between tracking and mixing.
Mastering is the process of turning a song or collection of songs into a final master for manufacturing so that it translates well across systems: CD player, radio, computer, car stereo, phone, etc.
The process involves:
- Balancing the level and tonal balance (EQ) of songs
- Controlling the dynamic range - how loud and quiet each section is, for the right musical balance of variety and power
- Compressing, EQing, M/S Processing and Limiting so the song is polished
- Creating a secure, reliable manufacturing master, including PQ information, UPC/EAN codes, ISRCs, CD-Text
This can vary from being a very subtle process, involving minor tweaks to polish the existing mixes, to occasionally being a complete rescue mission for problem songs, or where detailed restoration is needed.