Companion Cube/Music

Examples of Companion Cubes in Music include:

Neil Diamond's "I Am...I Said" has in its chorus the line And no one heard at all / Not even the chair. While this is usually dismissed as being just an incredibly Painful Rhyme, Diamond himself has stated that the song was written at a time when he was in a hotel room feeling incredibly lonely, to the point where he really did regard said chair as his sole companion.
Yelle's "Best Friend" in the song "Mon meilleur ami". Her vibrator.