def center_of_effect(cloud, duration):
    """
    The center of effect condenses musical information
    in the spiral array by a single point.

    Parameters
    ----------
    cloud : 3D array
        Array containing the coordinates in the spiral array
        of the notes in the cloud.
    duration : array
        Array containing the duration of each note in the cloud


    Returns
    -------
    ce : array
       Coordinates of the center of effect
    """
    return (duration.reshape(-1, 1) * cloud).sum(0) / duration.sum()