Stereo is a format that uses two channels, left and right, to express the position and the width of sound. Giving each side different level, timing, and frequency content lets you create an image with a center, a left, a right, and depth. In production it comes up with instruments, recording, spatial effects, and panning.
The role of the two channels
A stereo signal consists of a left (L) and a right (R) channel. If both carry the same content, it is heard as a mono component located in the center. When there are differences between the sides, you perceive width and position. In a DAW you can check a stereo signal on a pair of meters or on a two-circle input display.
Relationship to panning
Panning a mono track left or right sets its position in the stereo field. On a track that is already stereo, you are working with the balance and the width between the sides. Simply pushing everything far left and right can leave the center empty or make the sound lopsided on one speaker, so decide the position of the leading elements first.
Ways to create width
Common approaches include layering separate takes on each side, recording with a stereo mic, using short delays or reverb across the sides, and using stereo instruments. Bigger differences between the sides do not always mean a wider sound. If phase differences get too large, the sound can thin out in mono playback.
Check mono compatibility
Smartphones, small speakers, and shop sound systems may play back with the sides summed to something close to mono. Switch to mono during the mix and after export, and confirm that important elements such as kick, bass, and vocal do not disappear or drop drastically in level.
Choosing between them in production
Keeping the low end and the core elements of a song centered, and creating width with decorative sounds and spatial effects, makes it easier to hold the balance. Whether you leave material in stereo or fold it to mono depends on its use. To convert a stereo file to mono, you can use the audio format converter tool.
