import operator


def gen_concordance(song_list):
    """
    Generate a concordance of words in song titles.

    Parameters:
        song_list -- list of song titles

    Returns:
        A structure whose entries are indexed by words.  The value of each
        entry is the number of times that word appears in song titles.
    """
    final_list = list(set(song_list))
    concordance = {}
    for song in final_list:
        for word in song.split(' '):
            windx = word.lower()
            indx = ''
            for charcter in windx:
                if charcter in 'abcdefghijklmnopqrstuvwxyz':
                    indx += charcter
            if indx in concordance:
                concordance[indx] += 1
            else:
                concordance[indx] = 1
    sorted_info = sorted(concordance.items(), key=operator.itemgetter(1))
    return sorted_info