After tracking is complete, the recording engineer works with the producer and artist to mix each song or section of the recording. The mix is broken down into at least two tracks, however many times the recording engineer uses more than two tracks. Multiple tracks allow the recording engineer greater ability to adjust the interrelationship between leads and rhythm.
After the initial mixdown, the recording engineer will perform editing and pre-mastering. This may include putting the songs into the desired order for an album. This process is known as sequencing. Next, the recording engineer performs pre-mastering, which includes dynamics processing, leveling, equalization and noise reduction.
It is important for recording engineers to use high-quality audio monitoring equipment when mastering audio. A high-resolution monitor system allows the recording engineer to make the subtle processing decisions necessary when mastering a recording. Monitor speakers should have wide bandwidth, high headroom and extremely flat frequency response. Additionally, the monitoring environment is also critical for recording engineers. The mastering room should be extremely quiet. Noise-producing equipment should be located in a separate room. Significant obstacles between the monitors and the listener should be eliminated.
Clients hire recording engineers to verify and obtain proper tonal balance in their music. Recording engineers do this through equalization, which is the manipulation of specified frequency ranges. In order to locate a problematic frequency range in the audio, recording engineers should start with a large boost and fairly wide parameter. The recording engineer should then sweep through frequencies until resonance is most exaggerated, which will alert the engineer to which frequencies should be lowered. Recording engineers with a musical background may use a keyboard and relative pitch to determine which frequencies are problematic.
Recording engineers must have excellent listening skills in order to professionally master audio. Ear training is an important technique that recording engineers use to increase their listening skills and widen their audio mastering vocabulary. Ear training teaches the recording engineer to become more aware of subtleties of sonic and musical reproductions. A core proficiency for recording engineers is recognizing frequency ranges. Ear training exercises should test the recording engineer's ability to recognize specific frequencies.