How to set the audio side (L / R) volume separately?

I need to set the balance volume of each side L/R, but i dont find any api or function to do that.

can anybody help me?

i have the same doubt.

i tried with play at position and pan but dont work.

Someone can help?

more details: is one audio, with pan set on audacity i want set the volume of audio sound for each headphone side

like the balance option on windows

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Someone can help ?