Stereo narrowing can be used to create a sense of closeness, intimacy, and focus in a mix. It can also help to avoid phase issues, clutter, and masking among the different elements of a song. To use stereo narrowing in a mix, start by using mono or near-mono sources for low-frequency and rhythmic elements such as bass, kick, and snare. This will create a sense of solidity and power while avoiding phase issues that can cause cancellation or thinning of the sound. Then use center panning or slight panning for important and dominant elements like vocals, leads, and solos. This will create a sense of focus and clarity, while avoiding masking or competing with other elements that have more stereo width. Finally, use stereo reduction or collapse tools to narrow the stereo width of a sound source. This will create a sense of intimacy and coherence while reducing the level, delay, or phase difference between the left and right channels of a sound source. You can also use these tools to fix or enhance stereo recordings that have unwanted or excessive stereo width.