def _clean_lyrics(lyrics):
    """
        Removes punctuations and lowercases the string.

        Parameters
        ----------
        lyrics : str
            lyrics for a single song
        Returns
        -------
        str
            String if there is text
        None
            Returns None if empty string
            
    """
    if  500 < len(lyrics) < 15000:
        lyrics = lyrics.replace(",","")
        lyrics = lyrics.replace(".","")
        lyrics = lyrics.replace(":","")
        lyrics = lyrics.replace(";","")
        lyrics = lyrics.replace("\"","")
        lyrics = lyrics.replace("\n"," ")
        lyrics = lyrics.replace("/","")
        lyrics = lyrics.replace("?","")
        lyrics = lyrics.replace("!","")
        lyrics = lyrics.replace("â€œ","")
        lyrics = lyrics.replace("â€˜","")
        lyrics = lyrics.replace("æ","")
        lyrics = lyrics.replace("ø","")
        lyrics = lyrics.replace("å","")
        lyrics = lyrics.replace("*","")
        return lyrics.lower()
    
    return None