Duplicating and time-shifting a track slightly does work to some degree, but more often than not it adds phase issues.

Duplicating, time shifting, and hard panning typically ends up making the earlier side sound a little louder than the later side, as your brain perceives the time and pan shift to be the sound source moving to the side, so you may have slightly better results by duplicating, time shifting, hard panning, and reducing volume of the earlier side slightly.

For best results though, as others mentioned before me, record it twice. Nothing, absolutely nothing, works better than that.

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