def __calc_absolute_times(note_on_events, conversion_factor):
    """calculates the absolute time of a midi event. Returns 
    a dataframe that includes the event times in microseconds.
    
    Arguments:
        note_on_events {dataframe} -- note event data
        conversion_factor {numeric} -- factor to convert to microsecs
    
    Returns:
        dataframe -- dataframe with added abs time columns
    """
    note_on_events['abs_time'] = note_on_events.time * conversion_factor
    
    return note_on_events