def shift(pos):
    """shift(pos) -> stereo

    Return a simple stereo shift. If pos is zero, there is no shift in
    origin; this returns the default stereo position. -1 means directly
    to the left; 1 means directly to the right. More extreme values
    recede into the distance.
    """
    if pos == 0:
        return ()
    return 1.0, float(pos)
