Step 5: Production B (Mixing)
The music is sent to an mixing engineer, where leveling of the recorded and/or sequenced audio is done, and effects such as equalization, compression and reverb are applied to give the track the desired sonic profile.
Once this is done, the mixed track will be "mastered", either by the same person, or by someone else who specializes specifically in mastering (recommended). This further enhances the audio, and optimizes the track for the system it is meant to be played back on.
If it is part of a soundtrack, the mastering will serve to make sure that all the tracks are consistent with each other and play back at compatible volume levels.