def artists_to_mpd_format(artists):
    """
    Format track artists for output to MPD client.

    :param artists: the artists
    :type track: array of :class:`mopidy.models.Artist`
    :rtype: string
    """
    artists = list(artists)
    artists.sort(key=lambda a: a.name)
    return ', '.join([a.name for a in artists if a.name])