In the Goldberg variations Bach combines two different types of variation: basso ostinato (the bass line of an opening Aria was taken for a base of the theme for the following variations) with genre (each variation has its individual character). The cycle is strictly organized. First, the work is divided into two large parts by the variation 16, which is a French Overture. Secondly, all 30 variations are divided into ten groups of three. Each three contains a genre piece in character of the Baroque suite dance (Sarabande, Minuet, Gavotte and so on), a virtuosic clavier toccata in the manner of Scarlatti and a canon with increasing interval of imitation. The author also retraces the history of understanding this structure by Bach scholars.