(null) is one of two options, depending on what you're listening to. (null) is either A) One of the many aliases of Noryokun, who released two singles under the name (null), one titled ???? on the now-defunct HTSB Sounds label, and JĹŤhatsu-on on the also defunct label Haylurion. B) You are seeing this because your music is not "tagged" correctly. Not the tags you can affix to a file here on last.fm, but rather the tags that can be edited within the file itself. Read more on Last.fm