Panning; stereo width
Placing each sound between your left and right ear, and deciding how far apart the whole mix spreads.
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What it is
Panning places a sound somewhere on the line between your left and right ear. Stereo width is how far the whole mix spreads across that line. Both are illusions built from level and timing differences between two channels, which is why they collapse the moment someone listens on one speaker.
The working convention: anything that carries meaning stays center. Dialogue, voiceover, kick, bass, and lead vocal go up the middle, and everything decorative fans out around them. Width comes from stereo recordings, doubled takes panned opposite each other, or stereo reverb on a centered source. Hard panning (all the way to one side) is a deliberate 1960s Beatles-style move, not a default.
The trap is fake width. Plugins that widen by flipping polarity or delaying one channel sound huge in headphones and then partly vanish when a phone or a smart speaker sums the mix to mono. Check every wide mix in mono before you ship. Second trap: heavy panning is disorienting for anyone with hearing in one ear, so keep essential information centered.
Ask AI for it
Mix this multitrack for stereo: keep voiceover, kick, and bass dead center; pan the two rhythm guitar takes hard left and hard right; place supporting percussion at roughly 30 percent left and right; use a stereo reverb on the centered vocal for width instead of a stereo widener plugin. Verify the whole mix in mono and report any element that loses level when summed.